Auto Service Professional - April 2021 by EndeavorBusinessMedia-VehicleRepairGroup

APRIL 2021 • VOL. 11, NO. 2

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APRIL 2021 • VOL. 11, NO. 2

THE TECHNICIAN’S RESOURCE

STOPPING POWER Success lies in details with brake work

+ Troubleshooting CAN faults Keep cool working on A/C systems Diagnostic Strategies 5

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Auto Service Professional > The Technician’s Resource

For Owners

For Managers

CONTENTS

For Technicians

April 2021 Vol. 11, No. 2

Departments 6

STRAIGHT TALK MOVING FORWARD: Training needs to be priority TECH TIPS From O-rings to LS Engine Lifter Service

TECHNICAL SERVICE BULLETINS From Fords to Toyotas

PRODUCTS New and innovative equipment for your tool chest and shop

AD INDEX Your connection to free information

Technical

SERVICING TODAY’S A/C SYSTEMS Changes come in details of modern vehicles

THE COMPLETE BRAKE JOB Success lies in the details

DIAGNOSING FAULTS IN HIGH SPEED COMMUNICATIONS Taking a methodical approach with the Controller Area Network

'IT AIN'T EASY' Diagnostic Strategies on Broken Cars

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S T R A I G H T TA L K

Worth the Time

Training is the Best Tool in Your Arsenal

S EVERYONE IN YOUR SHOP GETTING ALL OF THE training you need for to-

day and the future? Granted, given your shop’s busy schedule, it might be a challenge to fi nd the time, but as the saying goes, “It’s better to have it and not need it, than needing it and not having it.” Ever-advancing technological advancements demand that you keep pace. According to a recent automotive research study by IMR (an automotive industry research firm), the number one challenge faced by today’s automotive independent shops is staying up to date with advanced diagnostics, and finding the time for hands-on training and classroom/virtual training sessions. Given the “normal” daily workload faced by most technicians, this is certainly understandable. It’s no secret that parts and equipment manufacturers offer valuable training, but considering the exponential growth of automotive drivability and safety features built into today’s vehicles, it’s more important than ever for shops to find the time for ongoing training. While the internet can be a wonderful source for information, you can’t depend on the accuracy of many postings. Manufacturer-sourced training offered by trusted brands has become more vital than ever before. Instead of waiting for training sessions/programs to be announced, try to contact your manufacturer reps on a monthly basis to find out what training is available. Pushing for this information places you in the lead as opposed to wistfully waiting for a program to be announced. “The squeaky wheel gets the grease” is a tried and true saying that works. Let your reps know that you hunger for every bit of training that is available. The more you prod and poke, the greater your chances of being serviced. Staying asleep at the wheel for even a few months is an approach

Manufacturersourced training offered by trusted brands has become more vital than ever before.”

that can put your shop at a real disadvantage. Being lax in obtaining up-to-date diagnostic and repair is something that today’s shops simply cannot afford. Obtaining ASE certification has long been a proven standard of both obtaining knowledge and promoting your shop’s ASE certification to your customer base. According to a recent ASE release, among the 231,186 service professionals who have earned multiple certifications, 63,618 are certified as Master Automobile technicians, 2,950 as Master Collision Repair/Refinish technicians, 9.726 as Master Medium/Heavy Truck technicians, 1,101 as Master Medium/Heavy Vehicle technicians, 1,049 as Master Truck Equipment technicians, 927 as Master Transit Bus technicians and 1,465 as Master School Bus technicians. Depending on the technicians’ specific specialties/duties, certification in specific areas, such as engine repair, brakes, HVAC, light vehicle diesel engines, automatic transmission/transaxle, etc. are deemed necessary, the goal of working toward and maintaining a Master Tech level not only increases the shop’s ability to address multiple repair concerns but provides additional “bragging rights” in the eyes of customers. So, what are you waiting for? Even if your shop office walls may be decorated with previous certificates of training, time doesn’t stand still. The future is now.

M I K E M AV R I G I A N EDITOR

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OnlIne

THE TECHNICIAN’S RESOURCE

3515 Massillon Rd., Suite 350, Uniontown, OH 44685 (330) 899-2200, fax (330) 899-2209 Website: autoserviceprofessional.com

Publisher: Greg Smith gsmith@10missions.com Editor: Mike Mavrigian birchwdag@frontier.com Managing Editor: Ron Ledgard rledgard@10missions.com Senior Editor & Digital Projects Editor: Joy Kopcha, jkopcha@10missions.com Production Manager: Karen Runion krunion@10missions.com Art Director: Zach Pate Graphic Designer: Olivia Curti Production Artist: Lauren Coleman

CONTRIBUTORS Jeff Taylor, Diagnostics & Driveability Specialist Bill Fulton, ASE Master Tech Edwin Hazzard, Mobile Tech Specialist

ADVISORY BOARD Chris Chesney, CARQUEST

ASP’S WEBSITE IS THE GO-TO SITE FOR VEHICLE INFORMATION 24/7. Turn to it any time you need the latest technical service bulletins, in-depth technical articles and the newest products. Our site also features news from suppliers and manufacturers to keep you up-to-date on what’s happening in the automotive industry. Plus, go to our website to renew your subscription to ASP, read the digital version of each issue and sign up for a free subscription to our weekly eNewsletters!

Jake Sorensen, McNeil’s Auto Care Seth Thorson, Eurotech Automotive Donny Seyfer, Seyfer Automotive

SALES Dan Thornton / dthornton@10missions.com (734) 676-9135, mobile (734) 626-4950 Bob Marinez / bmarinez@10missions.com (330) 899-2200, ext. 2217, fax (330) 899-2209 Marianne Dyal / mdyal@10missions.com (706) 344-1388 Customer Service/Subscription Service Phone: (800) 260-0562 Email: subscriptions@autoserviceprofessional.com

EXECUTIVE OFFICERS President: Jay DeWitt Vice President: Chris Messer

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TECH TIPS 1

1. To remove the selector lever handle, turn the cover counterclockwise (you should feel two clicks). 2. Inspect the white plastic release rod for burrs, and smooth out at the area circled in red. 3. Apply grease to the top area of the plastic release rod.

SMART CAR SHIFTER If a customer complains about a stiff shifter release button in a Smart car (0.9L engine with dual clutch automatic transmission), this may be caused by an incorrectly engaged release mechanism in the selector lever knob and/or by a fine burr on the plastic cap on the release rod in the gearshift lever. 1. Check the position of the release button in the selector lever handle. Measure the gap at the bottom between the knob and the button. If the gap is less than 1mm, the gap is OK. If the gap is greater than 1mm, replace the selector lever knob. 2. Regardless of the measured gap, if the button appears stiff, remove the selector lever handle by turning the cover two clicks to the left (counterclockwise about 30 degrees) and remove the knob. 3. Smooth the release rod using 120 grit abrasive paper. 4. Apply Optitemp LG2 grease to the smoothed white release rod and reinstall the knob.

ESCAPE PLAN If you’re dealing with a 2017-2018 Ford Escape equipped with a 1.5L or 2.0L engine with the MIL on and the PCM has stored DTCs P0034, P023A, P0245, P0480, P0481, P0645, P06Ao, P06DB, P188D, P02602 and/or P2681, the vehicle may also exhibit an all-wheel drive fault warning and/ or traction control light on. If this is the case, inspect the 12A690 (1.5L) or 12C508 (2.0L) wiring harness from the battery junction box to the PCM for wiring retainers not installed correctly, allowing chafing to occur. Repair any damaged wires as needed.

O-RING BASICS Whenever installing any plug, fuel injector or sensor that features an O-ring seal, always lightly lubricate the O-ring prior to installation. If the O-ring is intended to seal engine oil, apply a thin coat of engine oil. If sealing coolant, apply a light coat of coolant. If designed to seal transmission fluid, apply trans fluid. If the application is fuel-related, apply either a light coat of fuel or a light coat of Vaseline (avoid lubricants that can damage the rubber, nitrile, etc. You get the idea. Installing an O-ring dry can lead to damage. Lubrication aids in guiding the O-ring into its recess with minimal resistance.

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A /C SYSTEMS

Servicing Today’s A/C Systems Changes come in details of modern vehicles

URING THE PAST THREE OR FOUR

DECADES, the basic theory of the automotive air conditioning system hasn’t changed a whole lot. What has changed is everything else that’s part of a vehicle’s air conditioning system. As we know the refrigerant has changed from R12 to R134a and now to R1234YF. These changes were made mainly as an environmental change. Besides the refrigerant change, the air conditioning systems have become more efficient and compact. The refrigerant capacity has grown smaller and the components have become smaller, as well. One reason is that the engine bays have decreased in size in order

Fig. 1: An HVAC control module that’s used on a 2003-2006 Cadillac

PHOTO COURTESY OF DORMAN PRODUCTS; ILLUSTRATION BY OLIVIA CURTI

BY EDWIN HA ZZ ARD

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Fig. 2

Fig. 3

to fit all the various components, plumbing, and wiring harnesses closer together. Servicing these modern air conditioning systems can increase labor costs to your customers due to the complexities and tight access it takes to reach these components. Along with the increased changes in the systems themselves, other changes like tooling and training have become a necessity to be able to keep up. Just like any other automotive system, it’s important to be able to stay on top of these changes so not only can you stay competitive but also profitable. As I stated earlier, the theory of automotive air conditioning systems still operates based on pressures of temperature, which hasn’t changed. In this article, we will look at some of the service techniques and proce-

Fig. 2: A Bosch ADS 625 full diagnostic scan tool Fig. 3: A 2014 Cadillac Escalade performing a HVAC actuator learn procedure

dures of working on modern air conditioning systems. Some of you have probably started seeing the R1234YF systems come into your service bays. Many of these systems may or may not still be under the manufacturer’s warranty. As you start seeing these systems more and more, an investment will need to be made in updated equipment, tooling and training. But this isn’t any different than what we’ve run into before with other automotive systems … correct? Today, as we drive our vehicles, a great many of us can enjoy the same comfort levels that we are accustomed to at home and at work. With the push of a button or the slide of a lever, we make the seamless transition from heating to cooling and back again without ever wondering how this change occurs. That is, unless something goes awry. The modern air conditioning system is controlled by a computer system. Most vehicles have an HVAC controller or control module. The HVAC controller which monitors its three subsystems of heating, cooling, and air conditioning work in tandem to make sure that customers have the utmost control over the climate of their cabin and are provided with clean air via ventilation. Monitoring a system of multiple sensors helps the vehicle’s central processing unit relay diagnostic information to the dashboard display. The other functions of HVAC systems in vehicles include a thermostat regulating temperature, and sensors that control moisture and humidity values in your vehicle’s cabin. Other common features include thermal systems control, seat- and location-specific heating and cooling, and automatic defrost settings utilizing fogging sensors. With all of these electronic add-ons, it’s important to have a capable scan tool that’s up to date. These systems are no different than any other systems on the vehicle as they have to be diagnosed in a similar fashion. Sometimes a simple fi x is just a software update to the control module. When using the new R1234YF refrigerant it’s important to follow the new procedures and guidelines that are put in place during service. For example, R1234YF is a new environmentally friendly refrigerant that has a 99.7% lower Global Warming Potential (GWP) than R134a. The new refrigerant is considered mildly flammable and has thermodynamic properties similar to R134a. Technicians must only use a SAE J2913 certified electronic leak detector when checking for leaks in an R1234YF A/C re-

PHOTOS COURTESY OF SOUTHEAST MOBILE TECH

A /C SYSTEMS

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Fig. 4

Fig. 4: A Robinar 34788ni recover and recycle machine for R134a Fig. 5: An electric fan clutch assembly used on a 6.7L diesel engine Fig. 6: A fan pulley that’s damaged on the edge

Fig. 5

Fig. 6

frigerant system. Other, non–certified leak detection devices could serve as ignition sources in the presence of hydrocarbons or other flammable refrigerants. Other leak detection practices for R1234YF involve the use of a leak detection pump. The R1234YF systems require the use of new, specific A/C compressor oils. The new refrigerant type uses ND-oil 12, which is actually a PAG 46 oil but with additives specifically for the R1234YF type refrigerant. One of the most critical things to remember when servicing a newer HVAC system is the equipment used to service these systems are totally different than their predecessors and the equipment is not to be shared, as cross-contamination will occur. Refrigerant recycle and recovery machines are separate and different all together. There are some manufacturers that have a dual purpose machine like the CPS products FX3030, which can recover, recycle and recharge both R134a and R1234YF refrigerants. Although the refrigerant capacities don’t seem to be that much different from one another, the cost per ounce of R1234YF is substantially higher. Cost can be about $10 per ounce. These systems are very expensive to repair so maintaining the vehicle is critical. There really aren’t any differences as to the way you service the R1234YF systems as opposed to the R134a vehicles. The components are basically the same. Certification is a must. The EPA made it mandatory that after January 2018 a Section 609 certification card will be required to purchase R-12, R134a, or R1234YF cylinders of two pounds or more. Distributors will be required to keep records of certified technicians purchasing refrigerants. When servicing a modern HVAC system, there are several components that need to be taken into consideration for proper operation to occur. The most important test you can perform on an HVAC system is a detailed visual inspection. Sometimes just a visual inspection will reveal the culprit right away. It doesn’t matter where you start your testing, but it’s important to cover all bases. Let’s start with the vehicle’s cooling system. The vehicle’s cooling system needs to be functioning the way it was designed. A cooling system that’s not functioning properly will affect the operation of the HVAC system. Having the proper antifreeze along with the correct ratio of the antifreeze to water balance will

PHOTOS COURTESY OF SOUTHEAST MOBILE TECH

A /C SYSTEMS

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Fig. 7: A Gates 91006 that you can use for measuring your alignment.

Fig. 8: A Mastercool 55200 electronic leak detector W/UV blue light

keep the engine not only cooling better, but the correct concentrate will prevent components from corrosion and premature wear. The components to check would be the water pump for leaks, pulley defects, bearing failure and proper coolant flow. Other components that work with the water pump assembly are clutch fans, fan blades and the fan shrouds as well. What do these issues have to do with the HVAC system? If the fan clutch isn’t working correctly to increase the fan speed, that’s needed to cool the refrigerant down as the high side refrigerant pressures start to rise in the condenser, then the high side pressure switch will alert the HVAC controller to shut the compressor down to prevent the refrigerant from boiling, which would significantly decrease the performance of the air conditioning system. The same goes for the electric fan module, as well. Fan belts such as a serpentine belt or v-belt need to be in good shape with the correct tension applied. A belt that’s loose, glazed or damaged will affect not only the cooling system but the air compressor, as well. The engine’s pulleys need to be free from dirt, debris and any irregularities that might impede operation. A chip in the pulley will cause premature belt wear as the belt will rub against the chip and start shredding the belt little by little. A good visual inspection is critical in stopping future belt failures. Pulley alignment is critical as well. Using a belt/pulley alignment tool will aid in checking for proper alignment.

When performing your visual inspection of the air conditioning system, be sure to be on the lookout for any oil residue on the fittings and connections which would indicate a possible leak in the system. When you are performing your leak check of the system, use your electronic leak detector and circle around the whole fitting or area where you see the oil residue. Hold the detector about a quarter of an inch away from the area to be tested. It is important that there isn’t any wind, fans running or any chemical odors near the leak area as that will throw off the testing. After you have performed your checks under the hood, don’t forget to check out the inside of the vehicle. Before you check the controls that operate the climate control settings take a good look at your windows. Yes, I did say windows. Check to make sure they roll up and down and when they are up check to make sure they seal correctly. Any window that doesn’t seal will let some of the desired temperature that is in the vehicle out. Using a smoke machine, you will be able to detect any sealing issues as the smoke will exit the vehicle. Also check the doors as they need to close and seal properly as well. Any leaks in these areas will decrease the performance of the HVAC system. Next check the controls of the climate control panel. Make sure all buttons work and that each selection is giving the desired results. Buttons, LED displays and manual sliding controls will wear over time. Using a scan tool on the newer systems will allow you to run the

A good visual inspection is critical in stopping future belt failures.

PHOTOS COURTESY OF SOUTHEAST MOBILE TECH

A /C SYSTEMS

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Fig. 9: A Redline smoke pro leak detector used in leak finding

end result needs to be the same. Fixing the customer’s vehicles right the fi rst time will not only keep them cool but will keep them coming back should they need your services at a later date. Repeat customers is what we all strive for. Having the proper training, top notch equipment and a logical diagnostic approach will keep your service bays full and your customers coming back. Edwin Hazzard owns South East Mobile Tech in Charleston, S.C., which is a mobile diagnostic and programming service providing technical service to many automotive and body repair shops. He has 38 years of experience in the automotive industry. He currently is an automotive trainer, a board member of TST (Technician Service Training), a member of the MDG (Mobile Diagnostic Group), a member of the Professional Tool and Equipment advisory board for Pten magazine, a committee member of Nastaf and is a beta tester for multiple tool makers.

PHOTOS COURTESY OF SOUTHEAST MOBILE TECH

Fig. 9

actuators in their full ranges. Some scan tools will let you calibrate the actuators, if needed. Many manufacturers make it mandatory to perform a calibration test after installing a new actuator. That is why having a capable scan tool is so important these days. Another thing that you will want to do on older systems that work off of the vehicle’s vacuum supply is to listen for a vacuum leak. If you hear one but can’t see it then using the smoke machine on the system will reveal where your leak is coming from. Don’t forget to check the controls for the rear seating. Some vehicles have auxiliary controls that control temperature and blower functions. One last thing I would like to mention for vehicles that have a lot of the high-end options would be to check the operation of heating and cooling seats. These, too, are part of the vehicle’s creature comfort amenities that also adds in the overall comfort of the vehicle owners. These are just some of the items that need to be checked while servicing the vehicle’s HVAC system. The important thing to remember is to pay attention to the details and don’t overlook the obvious. The way I go about diagnosing an HVAC system is, as I mentioned earlier, is to perform a complete visual inspection before I even attempt to hook up a set of gauges or even a scan tool. Your diagnostic approach may be different than mine, but the

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THE COMPLE TE BR AKE JOB

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The Complete Brake Job Success lies in the details B Y M I K E M AV R I G I A N

RAKE SYSTEM SERVICE IS PERHAPS THE MOST CRUCIAL ASPECT of vehi-

cle service. If the engine won’t start, the customer is stranded. If the engine or transmission causes a surge or poor acceleration, the customer is annoyed. But if the vehicle won’t stop, that’s a big problem.

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When wheels are installed, the fasteners must be tightened in an even pattern to distribute clamping load, and must be tightened to the correct torque value in a consistent manner. Unequal tightening of the fasteners can easily result in undue and uneven stress to the rotor hat, potentially causing distortion/warp at the rotor disc surfaces. Naturally, a distorted rotor will lead to a bouncing/shuddering brake pedal, as well as uneven wear of the friction surfaces. Never use an im-

pact wrench to tighten wheel fasteners, even though you view this as a time-saving approach. Set the impact wrench aside, grab your (calibrated) torque wrench and tighten the fasteners properly to specification. Yes, this requires a few additional minutes, but it can avoid a comeback and a customer complaint.

PRE-INSTALLATION WASH Regardless of using a new or used rotor, always clean the rotor. That does not mean simply spraying the surfaces with a fast-evaporating brake cleaning solvent. While spray brake cleaning solvent is viable and certainly helps to remove surface contaminants, it’s best to hand-wash and scrub the discs with a mix of hot water and Dawn dishwashing liquid and a clean nylon brush. Why do I specially suggest using Dawn? While I’m not a chemist and I don’t pretend to know what the formula is, Dawn is simply the best soap I’ve ever APRIL 2021 | A SP

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THE COMPLE TE BR AKE JOB

NEW STOCK ORDER FEATURE AVA I L A B L E AT F I R S T C A L LO N LI N E .C O M KEY FEATURES: • Stock order management • Indicates any inventory stocked at customer’s location in catalog lookup • Simplifies replenishing stocking inventory

Fig. 1: Proper brake service relies on understanding how the system operates and the use of precision measuring to inspect for disc thickness, disc parallelism and lateral runout.

Find an item in the Catalog and ‘Add to Stock Order’

1 Fig. 1

Once an item has been added to a Stock Order, an indicator will be shown on the Parts Catalog. This indicator shows the total number of Stock Orders that contain the item.

used for these applications, and it works well for removing oils and particles from the machined surfaces. You can certainly follow up with brake cleaning solvent but don’t rely on the solvent alone. Seriously, wash with Dawn and hot water, followed by a hot water rinse, followed by a cold water rinse (this aids in slowing down surface flash rust), then dry thoroughly. Once clean, wear clean disposable gloves while handling to prevent surface contamination. Rotor disc cleanliness is a critical aspect of proper brake service.

ROTOR RUNOUT AND THICKNESS VARIATION 2

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Whenever servicing brake rotors, always take the time to make a few measurements, even if the customer hasn’t complained about a bouncing brake pedal. Measure lateral runout, disc thickness and measure for thickness variation. Poorly machined or abused rotors, or rotors that have been warped as a result of uneven or over-tightening of the wheel fasteners can easily create a pulsating brake pedal. Aside from the

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Fig. 2 Fig. 2: Check rotor disc thickness with a micrometer. This allows you to determine if the rotor has worn beyond the recommended minimum thickness limit. If brake vibration is a concern, in addition to checking rotor lateral runout, a check of rotor thickness for variations can help to determine rotor condition.

Fig. 3

annoying feel of this, if the pedal is pulsating/bouncing, this means that the pads are not in a consistent full contact with the disc surface, which results in a varying contact patch between the disc and pad, which reduces braking efficiency. Measuring lateral runout is a simple process, and there’s no reason to avoid the task. With the wheel removed, install ALL of the wheel fasteners to solidly secure the rotor to the hub. In-

Fig. 3: While a “traditional” micrometer will feature two opposing flat anvils, an ideal type of rotor tool is a digital caliper that features a flat and an opposing pointed anvil.

stalling only two or three fasteners can result in an erroneous runout reading, which can easily fool you into thinking that the rotor has more runout than it actually has. This is especially critical when dealing with thin-hat rotors. Uneven and incomplete deflection at the hub can easily result in warped discs that display excessive runout. Always install and fully torque to specification all of the wheel’s fasteners. In order to avoid damaging the nut seat surfaces, it’s also a good idea to install conical washers between the nuts and rotor hat surfaces. As an example, by installing only two nuts on a five-bolt hub, you might obtain a runout reading of, say, 0.005 inches. By installing three nuts the reading might be 0.003 inches. But by installing all five, the reading may be 0.002 inches, which would be within spec. Mount a dial indicator to a stationary area that doesn’t move in relation to wheel rotation (frame, strut, etc.). Dial indicator mounts are available with magnetic bases or clamp-on designs. Position the dial indicator’s plunger at 90 degrees to the disc surface, and push the plunger in to provide about 0.050 inches preload. Then zero the gauge face. The plunger should feature a small roller bearing at the tip to provide a consistent reading. The plunger tip should be placed about ½-inches inboard from the outer edge of pad contact. Slowly rotate the rotor and locate the low spot, then zero the gauge again. Using a Sharpie, make a reference mark on the disc at the lowest reading location. Slowly rotate the rotor, observing the gauge, noting the highest reading. The difference represents the amount of runout. Vehicle manufacturer specifications may vary, but as a rule of thumb, the maximum allowable runout is about 0.001 inches to 0.002 inches for most applications. Depending on the rotor design, you may be able to correct for runout using an on-car lathe, or you may need to simply replace the rotor. However, before replacing a rotor that you suspect of having excess runout, make a matchmark on the rotor hat and a corresponding wheel stud, then remove the rotor and reinstall at the next clockwise position and re-check runout. You may have a situation where stacked tolerances between the rotor and the hub are creating the excess runout. Continue to relocate the rotor on the hub, checking runout with each change. You may

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be able to install the rotor with the high point of the rotor aligned with the low point of hub runout. Measure disc thickness, but avoid making any decision based on only one measurement location. Measure for disc thickness in eight locations. Refer to the minimum service limit (this should be visible on the rear cavity of the rotor hat). Even if one measurement location is within the allowable thickness, measuring for thickness variation at several spots may locate a thickness that is too close to minimum. This is sort of a double-check of findings that result from checking runout. Generally speaking, allowable thickness variation should be no more than 0.0002 inches (some OEs may spec a tolerance range of 0.001 inches to as little as 0.0004 inches). It’s best to monitor both runout and thickness variation at the same time. Checking lateral runout and thickness variation applies to all vehicle applications, and should not be limited only to vehicles that exhibit a brake pulsation issue. If the caliper is mounted incorrectly (damaged mounting bracket, etc.), this can place the pads at an angle that is not parallel to the rotor disc. As the pads wear, they will wear unevenly, possibly resulting in a taper wear. This places unequal pressure at the rotor, which can lead to uneven rotor wear (thickness variation). Be aware that when correcting rotors using an oncar brake lathe of the need to prevent metal shaving/ particles from contaminating ABS wheel speed sensors and tone wheels. Metal debris can be magnetically attracted to these surfaces, which can lead to false codes and intermittent ABS modulation. After rotor resurfacing, clean the sensors and tone rings, rotors, axle, etc. of any debris. Soap and hot water work well. Don’t apply compressed air to blow particles away, as this can cause the particles to expand contamination.

CALIPERS A brake caliper is “simply” a rigid housing that contains one or more pistons that move inward under hydraulic pressure to make the pad friction material contact the rotor disc surface. Sounds simple enough. However, even the best quality new caliper can’t operate efficiently if mounting procedures aren’t followed. Depending on the style (floating or fixed), the caliper must be mounted so that the pads are parallel to the

Fig. 4: The machined grooves seen on this Dodge Charger police car aid in self-cleaning the pads. The increased surface area created by the grooves also helps to dissipate rotor heat. If the vehicle was originally equipped with grooved or slotted rotors, it’s best to replace them with identical style rotors. Fig. 5: The use of an on-car brake lathe can cure an annoying pedal pulsation issue. Rather than truing a rotor that has a bit of lateral runout or thickness variation, machining a rotor on-the-vehicle eliminates variables such as potential hub runout. Once machined, the rotor must always be installed in the same clock position.

Fig. 4

Fig. 5

brake rotor disc. If a caliper is mounted without attention to the attachment points (rust/corrosion on mounting surfaces, etc.), this can create a non-parallel result, allowing the pads to contact the rotors at an angle, minimizing full pad contact. This results in less than efficient braking performance and taper-wears the pad friction material. Floating calipers that are attached to a caliper bracket rely on a pair of pins that allow the caliper to slide in/out. As the brake pedal is APRIL 2021 | A SP

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applied, hydraulic force pushes the piston and inboard pad toward the rotor disc, causing the caliper to slide inward, allowing the outboard pad to contact the rotor. If the pins are rusted, pitted, and have less than a smooth surface, the caliper will either cock (due to unequal sliding action between the two pins) or drag and result in insufficient pad pressure at the rotor and/or not retract when the pedal is released, resulting in the pad(s) dragging against the rotor, causing premature pad wear, elevated brake temperature and likely glazing of the rotor surface. Failure to clean rust buildup and properly lubricate caliper brackets is a major cause of brake noise, premature wear and increased

Fig. 6

Fig. 6: Prior to replacing pads, the caliper pistons must be retracted in order to provide room for the new and thicker pads. Never use channel pliers directly against the piston surfaces. Place a spare pad or flat heavy gauge steel plate against the pistons and use a C-clamp to compress, or use a dedicated piston compressor tool that engages the pistons with a flat plate. Using pliers directly against the pistons can easily cause piston damage. Fig. 7: Before installing the wheel, apply a thin coating of a high heat anti-seize paste to the hub, especially around the hub flange. This will prevent rust buildup and corrosion caused by dissimilar metals when an aluminum wheel mated to an iron hub, easing future wheel removal.

Fig. 7

stopping distance. When changing pads, the caliper piston(s) will have moved further outward as the old pads become thinner. In order to install the caliper now equipped with new and thicker pads, the piston(s) must be compressed in order to provide the proper clearance for pad-to-rotor disc installation. Avoid using large channel lock pliers to push a piston. This can cause the piston to slightly cock in its bore, and you stand a chance of damaging the piston contact face and potentially tearing the piston seal. Rather, use a dedicated piston compressor tool that provides a full-width flat face against the piston(s). If the old pads have experienced severe wear and have become very thin, the piston(s) have been operating beyond their intended bore path. If the pads have been worn thin, an increased area of the piston(s) has been exposed to the elements for a while, possibly allowing grit to build up on the piston walls. Pushing the dirty piston fully back into its bore can result in forcing grit into the seal and bore. This can result in a sticky piston that isn’t able to freely travel within its bore. If the piston(s) don’t travel easily and smoothly, it’s time to replace the caliper. Even if piston condition seems OK, always inspect the bleed valve to make sure it can be opened. If a bleed valve is severely stuck, you can be faced with a stubborn bleed, or even if it moves, it may not successfully seal when closed. If you suspect a bad valve and were able to remove it, installing a new valve may or may not provide a fix, depending on the condition of the caliper’s female threads and valve seat. Rather than wasting time and effort to repair, just replace the caliper. Also, check the hex size of all bleeder valves before you begin installation. It’s common, especially for some remanufactured calipers, to have bleed valves that feature a different hex size. It can make you crazy when faced with constantly hunting for a different line wrench size if each caliper has a different hex size. Knowing that you have the correct line wrench(s) handy from the start will save time and aggravation. In some cases, during the remanufacturing process, correcting damaged bleed valve female threads may have resulted in re-machining to a larger size, which may change the size of the hex (for example, original calipers may have featured bleed valves that require

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new boots, applying a thin coat of high-temperature caliper pin grease prior to installation. Never install guide pins dry.

PADS

Fig. 8

Fig. 9

Fig. 10

a 10mm line wrench, but the reman caliper may feature a bleed valve hex size of 5/16 inches, etc.). Check this from the start to avoid the need to travel back and forth to your tool chest. Sliding calipers that ride on smooth-wall guide pins must be inspected for cleanliness and smooth engagement of the pins to their bores. If guide pin boots are damaged, this is a clear indication that the pins are probably scored or rusty. Simply replace it with new pins and

Fig. 8: Prior to removing a wheel speed sensor, clean the area adjacent to the sensor to prevent debris from entering the exposed sensor mounting hole. Fig. 9: Tapered pad wear indicates caliper misalignment and is not to be blamed on the pads. Closely inspect the caliper mounting to check for a bent bracket, or debris or faulty hardware.. (Photo courtesy of NAPA) Fig. 10: Uneven pad wear, where the pads on the same axle show different rates of wear, indicate a sticking caliper.

Inspect the original pads for taper or uneven wear. Tapered wear indicates that the caliper is not aligned properly with the rotor disc. This could be due to sticking slider pins on a floating caliper design or a damaged/bent caliper mounting bracket. Note that another area to inspect are the caliper mounting bracket mating surfaces, as rust/debris may have been trapped between the mounting bracket and steering knuckle during a previous brake job, which may have cocked the bracket. If the pads on a floating caliper feature unequal wear, this is an indication that the caliper is not able to slide properly. This can prevent the outboard pad from making adequate contact with the rotor, relying on the inboard pad to do most of the work. The result: the inboard pad becomes more worn than the outboard pad. This is an example of why it’s so important to make sure that the caliper slide pins and bushings are clean and well lubricated. If unequal and/or excessive pad wear is found on a fixed caliper application, the guide ears of the pad backing plates may be sticking to the stainless steel guide/sliding clips, or the backing plate ears may be stuck against the caliper, causing the pad to be stuck against the rotor without being able to release the pad. Again, this emphasizes the need to clean/replace the pad hardware so that the pads are able to move freely within their operating range. Lube the friction surfaces (where the pad backing plate contacts the caliper and/or guides) with a silicone-based lubricant that offers a high melting point (a dedicated brake lubricant is recommended, designed specifically for pad/caliper lubrication). When installing new pads, be sure to remove all rust/debris from the caliper in those areas where the pad backing plate makes contact. Test-fit the pads to the caliper to verify freedom of movement. For instance, if the pad backing plate ears make significant contact with the caliper resulting in a too-tight fit, in some cases when using “bargain” pads, the backing plate ears may need to be carefully filed down to obtain adequate clearance. The best approach is to use only

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Fig. 11

high quality replacement pads from established manufacturers such as Brake Parts Inc., Wagner, Advics, etc., to obtain pads with tight quality control. Naturally, you never want to introduce any lubricant to the rotor disc of pad friction material. When installing new pads, make sure that your hands are clean and free of contaminants.

MASTER CYLINDERS When you encounter a low, sinking or spongy brake pedal, one suspect is the master cylinder. The cylinder may be bypassing, allowing fluid to leak past the piston seals internally, preventing a pressure buildup. This applies to all vehicles. Master cylinders feature lip cup seals. This design allows for the seal to improve as the pressure increases. Another feature of this seal is that it does not create a vacuum when the piston retracts. As the pedal is depressed, the piston is pushed in the forward direction. The lip cup seal, attached to the primary piston, generates pressure in the primary chamber first, which in turn, forces the secondary piston forward, building pressure in the secondary chamber. As the pressure increases in both chambers, the edges of the seal are pressed against the bore of the master cylinder. As pressure increases, sealing is improved.

Fig. 12

Fig. 11: Prior to installing any wheel speed sensor, make sure that the installation surface is clean and dry. Naturally, the sensor must be clean, as well. Be sure to lightly lubricate the sensor O-ring with a nonevasive lubricant in a pinch, Vaseline works well). Never attempt to install the sensor with a dry O-ring, as the risk of tearing the O-ring is high. Fig. 12: Inspect rotor vanes. Heavy rust or debris buildup in the vanes can severely limit the rotor’s ability to disperse heat.

In the manufacturing process, the testing procedure for master cylinders is done at low pressure. Lip cup seals are more likely to fail under low pressure. Perform an isolation test. Use the proper tool that won’t damage the flexible hydraulic brake hose, clamp off all brake hoses. Press down on the brake pedal, and if the pedal is low or spongy, remove the brake lines from the master cylinder, and install threaded plugs in the outlets (not plastic plugs). Press down on the brake pedal and release the pedal and wait approximately 10 seconds. This allows the quick takeup valve to open and the air to escape through the master cylinder compensating port, and the fluid in the reservoir to enter the bore of the master cylinder. Once air stops coming up into the reservoir, or the pedal becomes firm, apply light pressure to the pedal, and observe if the pedal continues toward the floor. When the master cylinder ports are plugged, and the air is bled out of the bore, the pedal should be high and hard under low pedal effort or high pedal effort. If the pedal sinks under either condition, the seal is damaged and the master cylinder should be replaced. A sinking or soft/spongy brake pedal is generally indicative of a master cylinder problem. The piston inside the master cylinder is likely allowing brake fluid to pass the piston seals, preventing the buildAPRIL 2021 | A SP

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Fig. 13: An accurate method of checking for hydraulic pressure at the calipers is to use a pressure transducer (pressure pad gauge).

Fig. 14: Install a pressure pad in place of one brake pad at each of the same axle’s brake locations. Orient the pressure pad between the caliper piston and the rotor.

up of braking pressure. The seals feature a lip cup style that generates sealing as pressure is increased. This type of seal does not create a vacuum when the piston retracts as the pedal is released. As the brake pedal is depressed, the piston pushes forward. The seals allow pressure to build in the primary chamber first (for front brakes). Pressure is then built up in the secondary chamber. Damaged or worn seals allow fluid pressure to leak past the seal and back into the fluid reservoir. When the brake pedal is depressed, bad seals simply allow the fluid to pump between the bore and reservoir instead of being pressure-forced through the lines to the brakes. If this is the case, and bad seals are the issue, no external leaks will result. Be aware that a cast iron master cylinder that features a poor quality casting may have casting pores that have opened up and result in external leakage. Always check for external leaks first. If the master cylinder housing shows signs of external leaks, we know that we have a bad part, so replace the master cylinder (with proper bench bleeding and system bleeding) before wasting time with further diagnosis. Even if we still have a poor pedal, at least we have replaced a known bad part. When diagnosing the hydraulic braking system, first perform an isolation test. Using the proper clamping tool, clamp off all four brake hoses. Depress the brake pedal. If the pedal is low or spongy, remove the brake lines from the master cylinder and install plugs at the line outlet ports. Depress the brake pedal again, and then release the pedal. Wait for about 10 seconds. This allows the quick take-up valve in the master cylinder to open, allowing air to escape through the cylinder compensating port, allowing fluid in the reservoir to enter the master cylinder bore. Once air stops coming up into the reservoir, or if the pedal becomes firm, apply light pressure to the pedal and observe if the pedal continues to drop to the floor. When the master cylinder ports are plugged and air is bled out of the bore, the pedal should be high and hard under low or high pedal effort. If the pedal drops, the seal(s) is damaged and the master cylinder must be replaced. Here’s a tip if you encounter a problem after installing a new master cylinder: As noted by Wagner Brakes, If a new master cylinder has been installed

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Fig. 15: Apply brake pedal pressure. The gauge will show the amount of pressure being produced. In this example, the gauge showed 980 pounds under initial pressure. As full force was applied, the gauge showed 3,500 pounds. Fig. 16: When pedal pressure was released in this example, the right front pressure quickly dropped to zero while the left front showed a very slow pressure drop.

Fig. 16

Fig. 17: The red needle on the right gauge remained at peak pressure as a reference, and the black needle dropped to zero when pedal pressure was released. Since the left gauge showed a very slow pressure drop, this indicated that the left front caliper was dragging/sticking. Fig. 15

Fig. 17

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Fig. 18

and the system is manually bled, the brake pedal is often depressed completely, moving the primary and secondary pistons to their extreme forward position. The primary piston may stick even though there are springs attempting to push it back into position. When a master cylinder is assembled, the seals and cylinder bore are lubricated for a positive seal. This, combined with any air trapped in the system can cause a vacuum lock in the cylinder. You can verify this condition by removing the master cylinder from the booster without disconnecting the brake lines. You may notice that the piston has not returned fully rearward and is not resting on the snap ring. Sometimes connecting a pressure bleeder and opening the wheel bleeder screws will cause the piston to return. You can also tap lightly on the housing, with bleeders open, to free the piston. Once the piston has returned to its correct position and air is bled from the system, the problem should not recur. As anyone who is experienced with servicing brake systems will attest, we need to be careful when choosing block-off plugs for master cylinder ports, since a variety of thread sizes and pitches are in use, as well as line-to-port sealing designs. Installing an incorrect plug can easily result in damaging the port threads, which automatically requires scrapping the master and obtaining another new unit. Improper bleeding procedures can also cause damage to a previously-good master cylinder. If a

Fig. 19

Fig. 18: Before replacing a master cylinder, inspect the depth of the piston’s pushrod cup, as a difference in cup depth as compared to the original master cylinder may require a length adjustment to the pushrod that exits the power booster. Start by measuring the distance from the master cylinder mating flange to the rear edge of the master cylinder. Fig. 19: Then measure the distance from the rear edge to the piston cup seat. Perform these measurements on both old and new master cylinders to see if they differ.

master cylinder has been operating correctly for many miles of use, and the system is then bled in the course of a normal brake job, the master cylinder’s piston seals can be damaged if the pedal is pushed fully to the floor during bleeding. Over the course of long term use, the piston inside the master cylinder travels a relatively short distance. If the system was poorly maintained and the brake fluid has absorbed excess moisture, the end of the piston bore may feature corrosion build-up in the end of the bore that normally never experiences piston travel. If, during the bleeding process, the pedal is pushed all the way to the floor, the piston is now pushed into the corroded area, possibly damaging the seal. To avoid this during a bleeding job, you can place an obstacle, such as a block of wood, under the pedal to avoid overtraveling the piston. Whenever servicing a vehicle’s brake system, examine the fluid in the reservoir. If it appears dirty, vacuum the fluid out of the reservoirs and replace with fresh fluid prior to bleeding. This reduces the risk of retaining contaminants in the hydraulic system. Always remember to bench-bleed any master cylinder that has been emptied of fluid. An improperly bled master cylinder will result in a low, soft pedal. This applies to a new unit as well as a used master cylinder that has been drained. This involves connecting temporary transfer tubes from the output ports into the reservoir(s), filling the reservoir(s)

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Fig. 20: Damaged master cylinder piston seals can result in internal leaks/bypass, preventing proper fluid routing and causing a soft or dropped pedal. (Image courtesy Brake Parts Inc)

and slowly pushing the piston fully forward and slowly releasing several times until all traces of air bubbles are eliminated. In some cases, even after bench bleeding via the output ports, it may be necessary to also bleed via the master cylinder’s bleed ports (if so equipped). Once all trapped air has been released, be sure to keep the fluid level in the reservoirs sufficiently high to avoid exposing the outlet orifices at the bottom of the reservoir wells before installing the master cylinder. Naturally, during system bleeding, constantly keep an eye on the reservoir fluid level to avoid running the master dry. A mention regarding master cylinder reservoir fluid level is worthy of note. A reservoir will feature min/max fluid level marks. Never overfill fluid above the max indicator. When brakes are applied and the friction material contacts the rotors and/or drums, heat is generated in the system, which causes the brake fluid to expand. The expanded fluid rises the level in the reservoir. If overfilled, the fluid can topout and have nowhere to go, resulting in potential brake drag, which results in overheated brakes and premature friction material wear. Always pay attention to the reservoir fluid level. If under-filled (below the min line), you run the risk of exposing the master cylinder ports dry, which reduces or eliminates hydraulic pressure as well as sucking air into the system.

Fig. 21

Fig. 22 Fig. 21: Example of a floating caliper. When the brakes are applied, the piston moves out toward the rotor disc and the inboard pad is pushed against the rotor. As this happens, the caliper slides inward, pushing the outboard pad against the rotor. If the caliper is not allowed to slide, the inboard pad will experience undue wear. (Image courtesy of Brake Parts Inc.) Fig. 22: Here’s an example of a fixed caliper design featuring inboard and outboard pistons. The caliper is mounted rigidly and does not move. Hydraulic pressure applied to inboard and outboard pistons allow both the inboard and outboard pads to move against the rotor simultaneously. Any unequal force at either pad can result from sticking pistons and/or limited/stuck pad travel where the backing plates drag/seize on guide surfaces. (Image courtesy of Brake Parts Inc.)

ABS GLITCH AFTER HUB REPLACEMENT? ABS light may be on and/or false ABS activation may occur following wheel bearing hub replacement on only one side of an axle. APRIL 2021 | A SP

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Fig. 23: Vehicles equipped with ABS may require very specific system bleeding procedures. Always refer to the OE service steps.

Fig. 24: If a new master cylinder piston does not fully return during bleeding, it may simply be temporarily stuck due to an internal vacuum lock. Use a pressure bleeder (with all wheel bleeders open) or lightly tap the cylinder housing to free the piston. Once the piston has returned to full rest against the rear snap ring, the issue should not recur. (image courtesy Wagner Brakes)

If you diagnose a bad hub bearing on one side of a vehicle and the ABS wheel speed sensor or tone ring is integral to the bearing, you may need additional repairs to restore proper ABS functioning. In many cases, replacing one hub bearing will cause the driver to feel ABS false activation when coming to a slow stop on dry pavement.

False activation is usually described as a pulse in the brake pedal when not expected. The pulsation comes from the ABS valves cycling the supposedly locked up wheel. This is due to the difference in signal strength from the wheel speed sensors (WSS) side to side. The problem is usually associated with air gap difference or wiring and/or connector integrity. In many cases, removing the WSS from the other side, if possible, and cleaning the mounting surface may repair the problem. The rust buildup actually lifts the WSS from the bearing, increasing the air gap and weakening the signal. Another possible issue is play in the bearing causing sine wave frequency change and or AC voltage variation. The new bearing will have little to no play, while the remaining hub has acceptable play but can still affect signal strength. Again, the difference in signal from side to side may be enough to trigger false activation. If WSS is integral and not serviceable, replacing the hub bearings in pairs may be the only answer. The ABS system is activating as designed, so no warning light will be illuminated in most cases. If the ABS warning light is on, chances are the issue is with a bad wheel speed sensor or a ground. Check the grounds first (ground cables grounded at the frame) for cleanliness. If rusted/corroded, remove, clean and replace. Next, per your scan tool’s direction for a specific wheel speed sensor location, check the wheel speed sensor. Inspect the sensor connector. Remove the sensor from its location and clean the mounting area. Check the sensor magnet for contamination. If the electronic brake control module (the ABS controller) is deemed faulty and requires replacement, after the lines have been disconnected and the unit removed, check and clean all line connectors. Make sure that threads are clean and that each connector freely rotates on the hard line. If rust/contaminants prevent free rotation, this can make reconnection difficult and can easily result in thread damaged and/or a fluid leak. After the new controller has been installed, the system must be bled, according to factory procedures. Always follow the specific procedure. Otherwise you may never bleed the system properly. Our thanks to the following for their input in this article: Advics; Raybestos (Brake Parts Inc.); Wagner Brakes

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D I A G N O S I S IN G FA U LT S

Diagnosing Faults in High Speed Communications Taking a methodical approach with the Controller Area Network B Y J E F F TAY L O R

THINKSTOCK

ANY TECHNICIANS START TO FEEL UNCOMFORTABLE ABOUT a diagnos-

tic situation if the scanner only shows U-codes, but if the scanner powers up but will not communicate, that uncomfortable feeling intensifies. Most techs are familiar with the multitude of communications networks used on today’s vehicles, but few are ever excited about diagnosing and repairing the most common network used today: Controller Area Network (CAN). CAN is a serial communication bus that is tough and

durable enough to perform well in the harsh environment of today’s automotive applications. Developed in 1984 by Bosch and Intel and first used in 1992, it has become the backbone for most of today’s vehicles’ high speed communications networks. CAN bus diagnostics are often challenging but are no different from other forms of diagnostics. Attention to detail is important and understanding how the circuits work is vital. CAN bus related complaints can cause a wide range of issues: warning lights, functionality issues, limited APRIL 2021 | A SP

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D I A G N O S IN G FA U LT S

Fig. 1

power mode, no transmission shifts, dead batteries, etc. The list of issues can be extensive. A CAN bus allows for multiple modules to be linked together, reducing the amount and complexity of the vehicle’s wiring. The CAN bus provides the manufacturer the ability to plug in modules as required and each of these modules is then able to communicate with all the other modules on the same CAN bus. Many of today’s vehicles will now have more than one CAN bus. There will be a high speed CAN bus for critical operations such as engine control, steering, brakes and other safety systems. But CAN is now used in many comfort, audio and interior control systems that previously used lower speed or manufacturer-specific network protocols. FCA (Fiat Chrysler Automobiles)/Ram uses a CAN bus called CAN IHS (CAN Interior High Speed). Honda, Toyota and others use a similar setup. The CAN bus uses a twisted pair of wires; a CAN Hi wire and CAN Lo wire to join modules together in a loop or bus as it is commonly referred to. CAN modules communicate by varying the voltage on these two wires. The data is sent along the bus in digital bits of information as a 1=Hi and 0=Lo. But twisted wires and modules are not the only pieces integral to a functioning CAN bus. There will also be two terminating resistors somewhere in the system, and testing for these resistors will aid in our diagnostics. Terminating resistors can be in a module, or they can be attached to the network remotely, but there will always be two. Service information or wiring diagrams will usually provide their

Fig. 1: This SRS module from under the seat of a GM was completely corroded and was stopping all communications on the CAN bus. The truck would still run and drive but the dash was lit up with warning lights. Fig. 2: This broken chassis ground strap on a 2016 GM G van with a 6.6 diesel was the cause of 34 different U-codes. The van would start and run and communicate on the CAN bus. The SES, ABS light and Emission warning (DEF system) were illuminated, and the ABS data showed a module voltage of only 9 volts, all because of a bad ground.

Fig. 2

location. BMW/Mercedes Benz often use remotely installed resistors and FCA puts theirs in their Star Connectors. Each terminating resistor is 120 Ω, and its purpose is to absorb any of the leftover message voltage that occurs after the message has been read and received by all the modules on the CAN bus. Because there are two 120 Ω resistors wired in parallel, the actual resistance of the CAN bus will be 60 Ω (this is important to remember). If one or both terminating resistors fails this may cause module communications issues, no scan tool communications and even a no-start. Terminating resistors are one of the first things to inspect when dealing with a CAN bus issue. Testing a CAN system requires tools that most tech have at their disposal. An up-to-date scanner, a good information system to show the network wiring diagram, module locations, module powers, grounds and terminating resistor location. A digital volt-ohmmeter (DVOM), digital storage oscilloscope (DSO), and DLC breakout box will simplify testing. Before testing for a CAN bus issue/failure, it is important to look at all the basics. These systems are sensi-

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tive to proper module voltages and module grounds. A thorough visual inspection is key: the simplest things can cause the most complex issues and most challenging diagnostics. But many times, these complex issues can come down to a simple solution. Bad grounds, poor battery voltage, poor connections, charging system issues, customer installed aftermarket devices and corrosion are some of the most common things that can cause CAN bus issues. After performing a full system scan of all vehicle modules (if the scanner will communicate), pay particular attention to which modules are able to communicate and which ones are not. This may point you in a diagnostic direction. If you know that the vehicle has ABS, but the ABS module is not showing up in a full module scan, it would certainly be the starting point in the diagnostics. If the ABS light is on and there are U-codes in other modules telling you that they cannot talk to the ABS module, a few simple tests for power, ground and communication lines will likely confirm the fact the ABS module has failed. The use of an OBDll breakout box can aid in initial testing. Although not absolutely needed, they are cheap and make pin testing of the CAN network much simpler, especially if you want to use a DSO, DVOM and a scanner simultaneously. A few simple tests can be done at the DLC using just DVOM, or a DVOM and a DSO combination. They are quick and can easily help in pinpointing a problem by verifying the CAN bus circuit integrity or the lack thereof. The following values are rules of thumb but if in doubt make sure to consult the vehicle’s manufacturer specifications. The pin numbers are for the standard wired OBDll compliant DLC. Test #1... Resistance testing between pin 6 (CAN Hi) and pin 14 (CAN Lo) at the DLC: to check the resistance of the CAN

bus we need to disconnect the battery and allow a few minutes for all the power to dissipate from the modules. • The spec is 58 to 64 Ω. • If the resistance is 116 to 128 Ω, there is an open circuit, and you are measuring the resistance of only 1 terminating resistor. • If the meter displays OL there is an open

somewhere before the first terminating resistor. • If the resistance is 0 to 2 Ω then CAN Hi and CAN Lo are shorted together somewhere. Test #2 resistance testing pin 6 (CAN Hi) and pin 14 (CAN Lo) for shorts to

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Fig. 3

Fig. 4

battery positive (pin 16) and chassis ground (pin 4) on the DLC, with battery still disconnected: • Connect the DVOM between pin 6 and pin 16; the DVOM should read OL. • Connect the DVOM between pin 14 and pin 16; the DVOM should read OL. • Connect the DVOM between pin 6 and pin 4; the DVOM should read OL. • Connect the DVOM between pin 14 and pin 4; the DVOM should read OL. • If the results of these tests are anything other than OL then there is either a short to voltage or a short to ground somewhere and that will have to be found and repaired. Test #3 Voltage testing at pin 6 (CAN Hi) and pin 14 (CAN Lo) on the DLC, battery connected KOEO:

Fig. 3: This screenshot is from the G van and shows two of the many U-codes that it had stored. Fig. 4: This is an example of a CAN bus splice pack. This is from a Sprinter Van; the NOx sensor module had shorted internally and melted the splice pack and caused the CAN bus to stop communicating.

To perform our final quick test at the DLC, we will reinstall the battery connection and with the KOEO (key on, engine off ) we will perform the following CAN bus voltage testing. Start by setting the DVOM to DC volts. Connect the DVOM or DSO between pin 6 (CAN Hi) and pin 4 (chassis ground) and then pin 14 (CAN Lo) and pin 4 (chassis ground). The following chart shows the expected results and what they could look like if the circuits are shorted to ground, battery or each other. FCA vehicles and RAM trucks have started to use a Security Gateway Module (SGW) that will typically not allow any testing of the CAN bus at the DLC. To test their CAN bus systems you will have to hook up your diagnostic equipment to the Star Connector in the dash or at the SGW. Other CAN buses used for interior controls, climate and comfort systems

CAN bus Circuit

Network sleeping

CAN bus idle

CAN bus active

CAN Lo shorted to ground

CAN Hi shorted to ground

CAN Lo shorted to battery

CAN Hi shorted to battery

CAN Hi shorted to CAN Lo

CAN Lo Pin 14 on DLC

2.4-2.5V

1.3-2.3V

0.3-0.5V

Battery Voltage

Battery Voltage less 0.75V

2.45V

CAN Hi Pin 6 on DLC

2.4-2.5V

2.6-3.5V

0.02V

Battery Voltage less 0.75V

Battery Voltage

2.45V

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Fig. 5: Simple tools that most techs have are what I use in the early stages of looking at a CAN bus or U-code issue. It is best to hook up to a known good vehicle so you can see what a good functional systems reading looks like before you have to diagnose a faulty one. Fig. 6: This is the OBDll breakout box that I use, they are inexpensive available online and form all the major tool suppliers and they make testing anything on the OBDll plug much simpler. Fig. 7: With my OBDll breakout box installed this is the expected result of the testing of the terminating resistors. Remember the battery must be disconnected to perform this test.

can be diagnosed in a similar fashion. Its not as convenient as the DLC, but testing is done in the same way. All CAN buses will have similar properties; a CAN hi, a CAN low and two terminating resistors across all manufacturers. These quick tests will often point our diagnostics in a certain direction. When these test results are combined with other information gathered, such as a module that is not communicating, U-code information, and other factors like past collision damage or aftermarket installed equipment, the problem can usually be isolated easier. But a worst-case scenario diagnostic method can still happen and that requires the actual unhooking of one module at a time on the CAN bus to see if the problem is resolved. Studying the CAN bus wiring diagram is important. Many European vehicles, older GM cars and trucks, Honda, Toyota and most FCA vehicles have CAN bus splice packs, and these can make module elimination much simpler. Late model GMs and Fords do not provide splice packs so it’s tougher on these to isolate each module. With my DVOM/DSO hooked up to the DLC breakout box I will observe the voltages on pin 6 and pin 14 while wiggling the wires, connectors and harnesses to watch for a change that could indicate a bad, loose or corroded connection before I disconnect each module. If there is no change, I will unplug that module, observe the results and if the expected values are not restored, plug it back in and move along the CAN bus wiring diagram to the next module and repeat the process. It’s important to note that I will also make sure that each module that I am disconnecting has proper battery voltage, good grounds and tight clean connections on the CAN bus lines, because if any of these three are missing, proper communications will not occur as well. Often simple equipment, proper testing, a thorough visual inspection, understanding how the system works and a methodical approach will show the cause of the CAN bus issue before it gets too complicated. Having a good game plan is vital in diagnosing any issue, but when it comes to a CAN bus problem it’s essential. Jeff Taylor boasts a 34-year career in the automotive industry with Eccles Auto Service in Dundas, Ontario, as a fully licensed professional lead technician. While continuing to be “on the bench” every day, Jeff is also heavily involved in government focus groups and serves as an accomplished technical writer.

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BROKEN CARS

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‘It Ain’t Easy’ Diagnostic Strategies on Broken Cars B Y B I L L F U LT O N

Y BEST FRIEND, THE LATE DAVID

WINGE, who was a world-class auto service technician, had a favorite quote: “It ain’t no damn easy thing.” That was in reference to diagnosing engine performance issues. I have spent many hours with David in the bay dealing with broken cars. Those of you who are in this industry as an automotive technician, know very well the truth in this quote and the challenges we face. It was in the early 1990s that the U.S. Department of Labor rated Automotive Technology third in technical demands for skilled trades. I wonder where we are now.

UNSPLASH.COM/@JAMIE452

A CASE STUDY The first case study that I want to share with you is a 2001 Lincoln Navigator with an intermittent no start and a misfire under road load conditions. My shop was the sixth and final shop challenged with this problem. The engine has been replaced first with a salvage yard engine with no improvement. Shop No. 5 replaced the engine with a rebuilt 5.4L engine; still with no improvement. Virtually all sensors, including all coils, all injectors, the converters, the PCM and fuel pump had been replaced before I took the vehicle in. The scan tool is our No. 1 choice of diagnostic weapons in the effort to scan for clues as to a trouble code or deranged data that might yield a clue. In the case of the Navigator, there were no codes and no conclusive data other than double digit negative fuel trim values before the PCM forced the engine back into open loop during the engine misfires under road loaded conditions.

Fig. 1: If the original catalytic converter was to have disintegrated, this is some of the catalyst substrate that would remain in the muffler. Fig. 2: Our discussion around mechanical integrity testing will revolve around the electronic pressure transducer versus the conventional compression gauge. There will be some limitations when using the conventional analog compression gauge.

Fig. 1

Fig. 2

When faced with a diagnostic dilemma, we make a decision on what testing we need to do and what diagnostic tester we are going to use. What you will see here are many tests conducted with a DSO, a current probe and a pressure transducer. You can easily come to a conclusion that I pyramided this vehicle with too many tests. Please keep in mind that five previous shops basically struck out in fixing this vehicle. I did not want to miss anything or leave a rock unturned. Please don’t get the impression that I bat 1.000 or that I walk on water because I don’t. I have had my share of trials and tribulations and have made my share of mistakes that come from working in this industry. My first encounter with the crank and intermittent no start occurred in the parking lot of my shop on a cold APRIL 2021 | A SP

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BROKEN CARS

Fig. 3: Wot cranking compression test using an electronic pressure transducer.

Fig. 4: Idle compression test with throttle plates closed using electronic pressure transducer.

winter day. Using an ST 125 spark tester indicated a good consistent spark. Removing a spark plug indicated wet and fouled plugs. This by itself proved to be very misleading. As you will see later, if I had weak or inconsistent spark my diagnostics would have been much easier. But keep in mind, the word intermittent plays here. While many intermittent no starts occurred or the engine missing under loaded conditions resulted in fouled spark plugs, there were a number of fouled plugs that were replaced. My first thought was that the engine might be starving for air. In as much as the MAF sensor was new and the scan tool showed more than 5 grams per second during cranking seemed normal but I felt it alone was not conclusive. I decided to conduct an exhaust back pressure test. My findings indicated a slight value more than 2 PSI during a power brake condition. Thinking that catalyst substrate may have broken apart from the original converters and ended up in the muffler, I removed the muffler and what I found is indicated in (Figure 1). Feeling pretty confident at this point, I decided to take a test drive if I were fortunate enough with a good startup. Much to my demise, the engine misfires were still obvious under road loaded conditions resulting in more fouled plugs. The initial assumption that the engine was starving for air was subjective. I simply needed to do more testing. Shop No. 5 replaced the salvage yard engine due to discovering two cylinders low on compression. However the rebuilt replacement engine exhibited the exact same symptoms. I was still not convinced that the engine was breathing properly, still entertaining the possibility that the fouled plug issue was due to the engine starving for air. The diagnostic weapons I chose at this point were the DSO and a pressure transducer (See Figure 2). The conventional compression gauge was only designed to conduct a WOT cranking compression test. My objective here is to verify good compression values during cranking, idle and WOT snap conditions. More important, I wanted to verify good cam timing as I was still convinced that the engine was not breathing properly and maybe due to retarded cam timing. Figure 3 indicates a good cranking compression value of 175 PSI. Figure 4 shows a 50 PSI value captured during idle conditions. The idle compression values will only be about 40% to 50% compared to the WOT cranking compression value. This is because the throttle plates

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are mostly closed during the idle compression test thus impeding the engines ability to breath. The WOT snap compression values matched the cranking compression values. Since the idle compression values seemed to be on the low side, this created the need to verify proper cam timing. This is another test we can do with the pressure transducer. As in the cranking compression test, we fit the electronic transducer to a conventional compression gauge hose. Make certain that you remove the Schraeder valve located in the conventional compression gauge hose, so that we can view all four strokes occurring and time the exact opening of the exhaust valve and the intake valves. The first step is to capture TDC events and then using the cursor measure the time between the two TDC events. Note in Figure 5, the value indicates 170 milliseconds. We know that the internal combustion engine has four strokes — intake, compression, power and exhaust. We simply divide 170 by 4 and find that a stroke will occur about every 42 milliseconds. Note Figure 6 where we have placed the 180 degree cursor at the 42 milli-second mark. The point marked EVO is the point of the exhaust valve opening. If you count the number of minor divisions between the TDC mark and the 180 degree mark, you will come up with 21 minor divisions. 180 divided by 21 will tell us that the crank turned 5 degrees per each minor division. Now count the number of minor divisions between the EVO point and the 180 degree cursor and you will see 8 minor divisions. Five degrees of crank rotation per minor division times the eight minor divisions tell us that the exhaust valve opening occurred 40 degrees before the BDC or 180 degree mark. Normally on most engines with fixed valve timing this point occurs very close to 45 degrees before BDC. The wave form tells us that the cam timing is proper and not the fault.

Fig. 5: Look closely. There are 8.6 grids are major divisions between the two TDC marks, which represent 720 degrees of crank rotation.

WHY DOES THIS REMAIN? We don’t have to monitor the point of intake valve opening since this is a single cam engine. The questions still begs us as to why we have the intermittent no start and the fouled spark plugs. The spark plug fouling problem occurred during the no start and also during test drives. Is the engine starving for air with a restricted exhaust or retarded valve timing? Since we are still using the pressure transducer let’s check for proper spark timing. Notice Figure 7. The number of minor divisions between the two TDC marks measure 56. 720 degrees of crank rotation is needed to

Fig. 6: Notice that there are 21 minor divisions between the TDC mark and the 180 degree mark. This again tells us that the crank turns 8 degrees per minor division. It appears that the EVO point occurred 5 minor divisions before the 180 degree mark. This represents an exhaust valve opening of 40 degrees BBDC.

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BROKEN CARS

Fig. 7

Fig. 8

complete all four strokes. We are using a secondary KV wand on top of the number 1 COP coil hooked to a spark tester indicating the firing event. The firing event occurred three minor divisions before TDC. Each minor division represents 12 degrees of crank rotation meaning the actual firing event occurred 36 degrees before TDC. Spark timing is good. At this point in my diagnostics I have eliminated both possibilities. When faced with these diagnostic dilemmas, have you ever had to walk away from the vehicle and spend some time planning your next diagnostic plan? I’ve done that many times at home in my easy chair where I can think clearly without interruptions. So where are we now? We know the exhaust is not restricted, the engine’s valve timing is correct and the spark timing is also correct. We are still stuck on the fact that the engine is either getting too much fuel or not enough air. I failed to mention earlier that the fuel pressure is within specs. In addition on a warm startup the injector on-time measured a normal value of 5 milliseconds. Could we be getting multiple injector pulses causing the extreme rich condition? We know that the PCM uses the CKP & CMP sensor input to determine the timing and sequence of injector pulses. Let’s take a dual trace DSO with the Pico scope to look at both the CKP and CMP signals captured during idle conditions. Notice the good CKP and CMP signals. The missing tooth on the reluctor wheel appears 45 degrees before TDC which is indicated by

the CMP signal. A CKP pulse occurs every 10 degrees of crank rotation. There were no erratic pulses from the CKP and the CMP sensors. Over the years, I have always been bullish on scoping the secondary firing event with specific focus on the spark line duration and angle. Let’s take a look of a good secondary ignition waveform, not from the Lincoln Navigator in Figure 8, but rather from a secondary lead from a GM DIS system. We are using the COP wand. We simply lay the probe on the secondary lead. Notice that at 1 millisecond per division the spark line duration measures 1.3 milliseconds. Now using the same COP wand laid on top of the coil, let’s look at a good secondary waveform from the Lincoln Navigator. The Ford systems will multi-fire the coils when engine RPM is below 1000 RPM. Notice the three good firing events in Figure 9. This waveform was captured from the Lincoln Navigator during idle no load conditions without a misfire occurring. The time base on the scope is 1 millisecond per division. The spark duration on the first firing event measures exactly 1 millisecond. The second and third firing event spark durations measure about .5 milliseconds each. All three spark durations added together become 2 milliseconds. Ford uses this strategy below 1000 RPM to ensure good spark propagation and a consistent flame front. Above 1000 RPM, the PCM shifts to one firing event per cylinder. Now let’s take a look at secondary with the engine missing in Figure 10. Notice the sloping

Fig. 7: If you look closely you will count 56 minor divisions between the two TDC marks. 720 divided by 56 tells us that the crank turns 12 degrees per minor division. It appears that the firing event occurred 3 minor divisions before TDC or a spark advance of 36 degrees BTDC. Fig. 8: The upward slope at the tail end of the spark line indicates a flame front has occurred.

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downward sparklines, which is an indication of a rich condition and a fouled spark plug.

NOW WHAT? Could it be possible that we are intermittently losing ignition and not the injector pulses which could cause the plugs to foul? Have you ever heard about the cardinal rule of electrical troubleshooting when it comes to intermittent electrical problems? It says,” Initially do not disturb the circuit!” Meaning ... don’t disconnect a connector and reconnect it. You may have eliminated the problem. The proper procedure when doing dynamic voltage checks is to back probe the voltage supply circuit with the circuit loaded and active in order to detect the loss of proper voltage supply. At this point, I violated that rule. Take a look at the fuse box. There is a 30 amp fuse that supplies voltage to the coils. Using my fused jumper lead I removed the fuse and jumped across the female terminals at the fuse box. My diagnostic weapon of choice at this point was to current ramp the coils with my low inductive current probes clamped around my jumper lead. At first, I noticed the engine started immediately and ran perfectly with no road loaded misfires. I’m ashamed to tell you that after removing the jumper lead and reinstalling the fuse the no start symptom returned, and if and when it did start, it still missed under road loaded conditions. With the jumper lead reinstalled, the engine started immediately and ran perfectly. The male terminals of the fuse and the female terminals of the fuse box were too loose, causing loss of B+ to the coils. You know they say hindsight is always 20/20. Looking back, I think of what I could have done, might have done or could have done to find the problem faster. Has that not happened to all of us? I could have taken two different approaches. First and foremost, I could have used a DVOM, and then back probed the plus side of a coil. By using the Min/Max mode of the meter, I would have discovered the loss of voltage supply to the coils when the engine began to miss or no start. In addition, I could have used my current probe and clamped around the red wire with the green tracer conveniently located on the fire wall, which is the feed wire for B+ to the coils. This would have prevented me from disturbing the circuit noting what happened when I used my jumper lead across the bad connection between male terminals of the

Fig. 9: This is a good secondary ignition waveform using COP wand on the first COP unit.

Fig. 10: The above waveform from secondary ignition indicates a fouled plug from the No. 1 cylinder.

fuse and the female terminals of the fuse box. Both choices would have verified the loss of coil saturation or loss of voltage supply to the coils resulting in no spark. However the injector pulses continued resulting in no spark and fuel fouled spark plugs. In closing, thank you for your commitment to this very resilient industry that more and more requires our dedication. Bill Fulton Ohio Automotive Technology

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TeChnICal ServICe

bulleTInS

Information courtesy of Mitchell 1

CADILLAC

HOT WEATHER VAPOR ISSUE 2013-2017 Cadillac and other GM vehicles may exhibit hesitation or stalling issues during ambient temperatures of 100 degrees F and higher, accompanied by DTCs P2635 and/or P018B. Excessively hot and sustained ambient temperatures can cause vapor buildup in the fuel feed line. Customers can be advised to utilize fuels with octane levels greater than 91, and to refrain from extended idle periods if possible. If the fuel pump is operating correctly, replacing the fuel pump will not correct the vapor condition.

FORD

DON'T GET FOOLED Some 2013-2019 Ford F-Super Duty trucks equipped with a 6.7L diesel engine may exhibit an illuminated MIL with only DTC P2074 stored in the PCM. This may simply be due to a dirty/clogged air filter. Replace as needed. Do not replace the PCM or MAF (mass airflow) sensor for this concern. Check the simple stuff first.

CHEVROLET

CHEVY SHIFT CHECK NISSAN This bulletin applies to 2009-2017 Chevy Equinox, Impala, Malibu and Traverse vehicles equipped with an automatic transmission. Some customers may comment that the check engine light is illuminated. In rare cases, they may also comment that there is no PRNDL display. When checking for DTCs, technicians may find P182E set as active or history in the TCM (transmission control module). 1. Verify proper shift cable adjustment. 2. Verify proper ECM Park/Neutral switch status in all ranges. 3. Verify proper internal mode switch (IMS) A/B/C/P parameters in all ranges. 4. Operate the vehicle within the conditions for running the DTC and freeze frame/failure records data in an attempt to duplicate the DTC. If the DTC does not reset, replace the IMS (lever, manual shift detent with shaft position switch assembly). If the DTC does reset, complete circuit/ system testing steps. If DTC U0101 is set as active or history in the EBCM (electronic brake control module), it should be ignored as it has been found to be falsely setting.

DOWN ON POWER This bulletin applies to all Nissan vehicles equipped with an electric throttle chamber) for example, 2015 Altima), where the customer complains of a lack or power/ poor acceleration. First check for DTCs and address as needed. Check to see if the driver has a habit of resting his/her foot on the brake pedal while driving. Advise the customer not to rest their foot on the brake while accelerating. Also, use CONSULT-III plus in Engine Data Monitor to check operation of the brake lamp circuit signal. Monitor the brake switch during the incident...it should be “OFF.” Causes of the brake switch ON condition can include an incorrectly adjusted brake switch or a damaged brake map wiring/circuit. Damage can cause a signal to the ECM to show ON when it should be OFF.

Visit autoserviceprofessional.com/TSB for additional service bulletins.

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prOduCTs

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Dana adds Spicer Select center support bearings coverage ••• Dana Incorporated has announced that new coverage has been added to its Spicer Select light-vehicle center bearings line, including high VIO (vehicles in operations) applications such as the 1999-2007 Chevrolet Silverado trucks, as well as fleet-managed, last-mile delivery applications like the Dodge and Mercedes-Benz Sprinter vans. This new coverage addresses the increased number of last-mile delivery vehicles on the road today. Premium-grade Spicer Select light-vehicle center bearings feature brackets made from high-quality steel that fit to original-equipment specifications and proper rubber hardness for each application, ensuring a smooth and quiet ride. DANA INCORPORATED spicerparts.com/spicerselect

Bosch, Mitchell introduce new target system for Static ADS calibration ••• Mitchell and Bosch Automotive Service Solutions introduced MD-TS21, the new computerbased target system that is designed to allow repair facilities to quickly and precisely calibrate front-facing cameras, blind-spot monitors and radar sensors in popular automobile models with ADAS. The MD-TS21 uses technology and industrial-grade digital cameras to automatically measure the distance and angles of targets in relation to the vehicle. With the help of guided lasers, technicians can easily adjust the target board and radar reflector positioning in minutes. The wireless tablet controls the system. MITCHELL mitchell.com/products-services/collision-repair-shop-solutions/car-diagnostic-system

New and innovative equipment for your tool chest and shop

Bosch Aftermarket adds new scan tool ••• Bosch Aftermarket announced its newest scan tool, the ADS 625X, is now available. The new ADS 625X is the most advanced OE-level vehicle coverage diagnostic tool, with scanning, live data access and complete bi-directional functions capabilities. This new tool includes the same great features as the ADS 525X for extreme speed, access, and flexibility to help resolve issues quicker. On top of that, the ADS 625X includes: * A larger screen display – 10-inch LCD vibrant highdefinition display. * Expandable memory – With a slot for an SD card. * Android OS 10+ – Allnew hardware and software technology. * Docking station. In June, the ADS 625X will be compatible with the DAS 3000 for full tatic calibration. BOSCH AFTERMARKET boschdiagnostics.com. APRIL 2021 | A SP

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Designed to pass. Built to last.

OTC equipment meets all ASME PASE-2019 safe lifting standards and offers a limited lifetime warranty.

IME LIFERTANT Y WAR

SEE THE NEW EQUIPMENT AT OTCTOOLS.COM

ED AND ST

ELEVATE TO THE BLUE STAR STANDARD

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APRIL 2021 | A SP

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PROJECT NAME

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TRIM

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