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2000 Saturn SC2 2000-01 STEERING Electronic - Saturn "S" Series

2000-01 STEERING Electronic - Saturn "S" Series

DESCRIPTION & OPERATION The Variable Effort Steering (VES) system, also referred to as an Electronic Variable Orifice (EVO) steering system, varies the effort required to turn the steering wheel based on vehicle speed. As vehicle speed increases, EVO system decreases the amount of pump fluid pressure applied to the steering gear. EVO system is controlled by Powertrain Control Module (PCM) located behind left end of instrument panel. PCM receives signals from Vehicle Speed Sensor (VSS) on transaxle. Based on VSS signals, PCM cycles EVO actuator on and off to control power steering pump pressure at the pump outlet hose fitting. See Fig. 1 . When EVO actuator is off (de-energized), full pump pressure is allowed through pressure line outlet to steering gear. When EVO actuator is on (energized), pump fluid bypasses pressure line outlet and is routed back into pump, decreasing pump pressure to the steering gear. EVO actuator cycling occurs at vehicle speed of 12 MPH or greater. EVO system has self-diagnostic ability that is part of PCM self-diagnostics. See DIAGNOSIS & TESTING . NOTE:

For information on base steering system, see POWER RACK & PINION SATURN "S" SERIES article.

TROUBLE SHOOTING Check power steering fluid level. Add fluid if necessary. Check pump drive belt for correct tension. See ADJUSTMENTS in POWER RACK & PINION - SATURN "S" SERIES article. Ensure Electronic Variable Orifice (EVO) actuator connector is secure and clean.

DIAGNOSIS & TESTING NOTE:

For additional information on self-diagnostic system (including diagnosis of codes not covered in this article), see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

Diagnostic Trouble Codes (DTC) are retrieved using a scan tool. Fault codes related to Electronic Variable Orifice (EVO) system are Powertrain Control Module (PCM) engine DTC(s) P0636 and P0637, which set when EVO circuit switches from low to high voltage. RETRIEVING DIAGNOSTIC TROUBLE CODES 1. Enter diagnostics using scan tool. Check for DTCs. If PCM DTC P0636 or P0637 is set, diagnose and repair problem. See DIAGNOSTIC TESTS . CAUTION: To prevent power steering pump damage during pump pressure testing, open valve on tester before starting engine. During testing, Helpmelearn November-05-07 7:35:12 7:35:09 PM

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2000 Saturn SC2 2000-01 STEERING Electronic - Saturn "S" Series

DO NOT turn steering wheel unless specified in procedure. 2. If no information flag or codes are set, disconnect high pressure line at power steering pump. Connect Power Steering System Tester (SA9134C) between power steering high pressure line and pump fitting. Set parking brake. Place transmission in Park (Neutral on manual transmission). Open valve on tester. Start engine. Allow power steering system to reach operating temperature (2-3 minutes). Ensure fluid level is correct. If necessary, bleed hydraulic system. See HYDRAULIC SYSTEM BLEEDING under LUBRICATION. 3. With engine idling, record power steering pressure and flow rate. If pressure is greater than 150 psi (10.5 kg/cm2 ), stop engine and check for restricted power steering hose. 4. Partially close valve until pressure is 700 psi (49 kg/cm2 ). Record flow rate. If difference between this flow rate and that obtained in previous step is greater than one gallon (3.8L) per minute, replace power steering pump ring, rotor and vanes. Check for worn or damaged pressure plate and thrust plates. Replace components or entire pump assembly as necessary. CAUTION: Pump will be damaged if tester valve is held closed for more than 5 seconds. 5. Completely close valve for a few seconds, and then open it. Do this 3 times, recording highest pressure obtained each time valve is closed. If readings are not within 50 psi (3.5 kg/cm2 ) of each other, replace flow control valve. See Fig. 1 . Ensure flow control valve moves freely in bore. 6. With engine speed at 1600 RPM, record flow rate. If difference between this flow rate and that obtained in step 3 is less than one gallon (3.8L) per minute, go to next step. If difference between flow rates is greater than one gallon (3.8L) per minute, remove and clean flow control valve. DO NOT disassemble valve. Ensure valve moves freely. 7. Turn steering wheel from stop to stop, recording pressure and flow rate at each stop. DO NOT hold steering wheel at stops for more than 5 seconds. If flow rate at either stop is less than one gallon (3.8L) per minute, go to next step. If flow rate at either stop is greater than one gallon (3.8L) per minute, steering gear is leaking internally. Replace steering gear. See POWER RACK & PINION - SATURN "S" SERIES article. Remove tester. Fill and bleed system. See HYDRAULIC SYSTEM BLEEDING under LUBRICATION. 8. Turn ignition off. Connect Tech 1 scan tool. Select EVO SUBSYSTEM from SPECIAL TEST menu. Open valve on tester. Start engine. Using Tech 1 scan tool, command Electronic Variable Orifice (EVO) actuator to provide FULL ASSIST. If flow rate is not 2.35-2.85 gallons (8.9-10.8L) per minute, replace EVO actuator on pump. 9. If flow rate is 2.35-2.85 gallons (8.9-10.8L) per minute, command EVO actuator to select NO ASSIST using Tech 1 scan tool. If flow rate is not 0.4-0.9 gallon (1.5-3.4L) per minute, replace EVO actuator. CLEARING DIAGNOSTIC TROUBLE CODES NOTE:

DTCs that are stored in general information are automatically cleared after 50 ignition cycles, or if power is disconnected from PCM.

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2000 Saturn SC2 2000-01 STEERING Electronic - Saturn "S" Series

When a DTC is set, PCM stores them in 2 different places: general information and malfunction history. DTCs stored in malfunction history can only be cleared using scan tool. To clear DTCs stored in general information, use scan tool, or disconnect battery for 60 seconds.

DIAGNOSTIC TESTS NOTE:

To identify circuits and terminals referenced in testing, see WIRING DIAGRAMS .

DTC P0636: LOW CIRCUIT CAUTION: To prevent damage to connector terminals, DO NOT probe PCM connector terminals at very end of terminal. Instead, backprobe these terminals, even when PCM connector is disconnected. 1. Connect scan tool. Drive vehicle at speed of 30 MPH or more while an assistant monitors EVO feedback. If feedback does not increase as vehicle speed increases, go to next step. If feedback increases as vehicle speed increases, problem is intermittent. Check for cause of intermittent problem (such as poor connections), and check system mechanical condition. 2. Turn ignition off. Using scan tool, monitor EVO SOLENOID - LOW VOLT test, while turning EVO SOLENOID on. If test fails, go to next step. If test does not fail and DTC still exits, problem is intermittent. 3. Disconnect EVO solenoid. Connect jumper wire between high and low EVO PCM circuits (Brown & White wires). Using scan tool, monitor EVO SOLENOID - LOW VOLT test, while turning EVO SOLENOID on. If test passes, replace EVO solenoid. If test does not pass, go to next step. 4. Remove jumper wire. Turn ignition off. Disconnect PCM harness connector. Check for continuity between EVO low circuit (Brown wire) and ground at EVO solenoid. If continuity exists, repair EVO low circuit (Brown wire) short to ground. If continuity does not exist, replace PCM. See appropriate REMOVAL & INSTALLATION article in ENGINE PERFORMANCE. Diagnostic Aids

Scan tool displays Electronic Variable Orifice (EVO) output and feedback values to assist in diagnosis of EVO system. When system is operating as it should, the following conditions will occur: z

z

When no output is generated by PCM (EVO actuator not cycling), output value indicated on Tech 1 scan tool will be 100 percent, and feedback value will be zero percent. When output is generated by PCM (EVO actuator cycling), output value will decrease, and input value will increase proportionally. For example, if output is 80 percent, input will be 20 percent, or if output is 20 percent, input will be 80 percent.

DTC P0637: HIGH CIRCUIT CAUTION: To prevent damage to connector terminals, DO NOT probe PCM connector terminals at very end of terminal. Instead, backprobe these terminals, even Helpmelearn November-05-07 7:35:09 PM

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2000 Saturn SC2 2000-01 STEERING Electronic - Saturn "S" Series

when PCM connector is disconnected. 1. Turn ignition on, with engine off. Using Scan Tool, monitor EVO SOLENOID - HIGH VOLT test, while turning EVO SOLENOID off. If test fails, go to next step. If test does not fail and DTC still exits, problem is intermittent. 2. Disconnect EVO solenoid. Connect jumper wire between high and low EVO PCM circuits (Brown & White wires). Using scan tool, monitor EVO SOLENOID - HIGH VOLT test, while turning EVO SOLENOID off. If test passes, check for tight connection at terminal. If test does not pass, go to next step. 3. Using DVOM, measure voltage on high EVO circuit (White wire), while turning EVO solenoid on. If voltage is not present, circuit No. 1876 is open, or terminal is too tight to PCM. If voltage is present, go to next step. 4. Connect test light between EVO low circuit (Brown wire) and battery positive terminal. If test light illuminates, EVO high circuit is shorted to voltage. If not, EVO low circuit is open or terminal connection is too tight. 5. Diagnostic Aids

Scan tool displays Electronic Variable Orifice (EVO) output and feedback values to assist in diagnosis of EVO system. When system is operating as it should, the following conditions will occur: z

z

When no output is generated by PCM (EVO actuator not cycling), output value indicated on Tech 1 scan tool will be 100 percent, and feedback value will be zero percent. When output is generated by PCM (EVO actuator cycling), output value will decrease, and input value will increase proportionally. For example, if output is 80 percent, input will be 20 percent, or if output is 20 percent, input will be 80 percent.

LUBRICATION HYDRAULIC SYSTEM BLEEDING NOTE:

If air was allowed into hydraulic system during servicing, bleed system. Aerated fluid, which is Light Tan in color, results in poor steering performance and causes pump damage.

1. Turn ignition off. Raise and support front of vehicle with wheels off ground. Turn wheels fully to left. If necessary, add power steering fluid to FULL mark on fluid level indicator. Turn steering wheel from side to side several times, but DO NOT touch steering stops. Add fluid, if necessary, to maintain level at FULL mark. 2. Start engine. With engine idling, add fluid as necessary. Return wheels to straight-ahead position. Lower vehicle. Continue to run engine for 2-3 minutes to bring fluid to operating temperature. 3. Road test vehicle. Check for leaks. Ensure fluid level is at FULL mark when fluid stabilizes at operating temperature. Helpmelearn November-05-07 7:35:09 PM

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2000 Saturn SC2 2000-01 STEERING Electronic - Saturn "S" Series

ADJUSTMENTS POWER STEERING PUMP BELT NOTE:

See ADJUSTMENTS in appropriate RACK & PINION article.

REMOVAL & INSTALLATION CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery. EVO ACTUATOR Removal

CAUTION: When removing Electronic Variable Orifice (EVO) actuator with Slotted Socket (SA9116C), DO NOT allow socket to become cocked to one side or actuator will be damaged. Disconnect negative battery cable. Remove power steering pump. See POWER STEERING PUMP . Remove electrical connector locating clip from EVO actuator. See Fig. 1 . Note position of discharge fitting and EVO actuator on pump for installation reference. Remove EVO actuator using Slotted Socket (SA9116C). Remove discharge fitting and 3 "O" rings, noting size and location of each "O" ring. Installation

1. Install "O" rings, in correct order, onto EVO actuator. See Fig. 1 . Install discharge fitting onto EVO actuator until fully seated. Correctly position fitting and EVO actuator onto pump. Tighten EVO actuator to specification using slotted socket. See TORQUE SPECIFICATIONS . 2. Position electrical connector so that it points to rear of pump, in-line with shaft. Install electrical connector locating clip. Install pump. See POWER STEERING PUMP . Fill and bleed hydraulic system. See HYDRAULIC SYSTEM BLEEDING under LUBRICATION.

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2000 Saturn SC2 2000-01 STEERING Electronic - Saturn "S" Series

Fig. 1: Exploded View Of EVO Actuator Courtesy of GENERAL MOTORS CORP. POWER STEERING PUMP Removal

1. Disconnect negative battery cable. Remove pump reservoir cap. Raise and support vehicle on hoist. Place drain pan under pressure and return hose fittings at steering gear. Disconnect hoses from steering gear and allow system to drain. 2. DO NOT rotate steering wheel, as fluid will be forced out of steering gear fittings. Using appropriate wrench, rotate drive belt tensioner to relieve belt tension, and then remove drive belt from pump pulley. On Dual Overhead Cam (DOHC) engine, remove steering pump-to-intake manifold bracket and steering pump-to-engine bracket. Helpmelearn November-05-07 7:35:09 PM

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2001 Saturn S-Series Service Repair Manual  

2001 Saturn S-Series Service Repair Manual  

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