How to Use This Chapter

This section uses “decision-tree” charts and symptom tables designed to take you from a symptom to a specific sequence of tests in order to isolate a failing component.

•Use the “TS1: START TROUBLESHOOTING” on page5-31 to guide you to the individual symptom chart you need.

•When you’re familiar with the symptoms listed, you may instead simply look up the symptom chart from the “List of Troubleshooting Charts/Tables” on page5-29

As you work with a troubleshooting symptom table, you may be instructed to test various electrical connector pins.

Every time you complete a troubleshooting procedure, make sure you follow the steps in the “END1: End of Troubleshooting Procedure” on page5-33.

If the troubleshooting symptom tables do not isolate the problem, or if the symptoms are not consistent or repeatable, go to “GEN1: General Troubleshooting” on page5-31. This chart will help you approach the problem in a systematic and logical manner.

Electrical Troubleshooting Guidelines

Many problems are caused by a faulty or dirty battery. Make sure the battery is clean. Check the electrolyte level and state-of-charge. See “Battery” on page6-4. Block the truck whenever a troubleshooting procedure requires turning the key switch ON. This avoids accidents caused by unexpected truck travel.

Unless otherwise directed, disconnect the battery connector when you check electrical circuits or components with an ohmmeter. Electrical current can cause damage to the ohmmeter.

Save time and trouble by looking for simple causes first.

Visually inspect all wiring and electrical components for:

•loose connections or connectors

•loose or broken terminals

•damaged terminals, blocks, or strips

•broken wiring and shorted conditions (especially those that are close to metal edges or surfaces)

Use an ohmmeter to check for wiring continuity and shorts.

For information on pin, connector, and harness connections, see “Wiring Harness” on page6-11 and “List of Electrical Symbols” on page5-8.

Checking for Shorts from Battery to Truck Frame

1.Press the red OFF (O) key on the keypad and disconnect the battery connector.

2.Using a voltmeter set on a 50 VDC scale. attach the leads as follows:

•negative (–) lead to an unpainted, grounded surface on the truck frame

•positive (+) lead to the positive battery terminal

The voltmeter must show no more than 3V.

3.Now attach the leads as follows:

•negative (–) lead to the negative battery terminal

•positive (+) lead to an unpainted, grounded surface on the truck frame

The voltmeter must show no more than 3V.

4.If you get more than a 3V reading in Steps 2 or 3: a.Remove the battery from the truck. See “Battery” on page6-4. b.Thoroughly clean the battery. See “Battery Maintenance” on page6-5. c.Reinstall the battery. d.Repeat steps 2 and 3 to see if this has eliminated the problem. e.If excessive voltage is still found, have the battery checked for internal leakage.

Checking for Shorts from Components to Truck Frame

1.Press the red OFF (O) key on the keypad and disconnect the battery connector.

2.Use an ohmmeter and measure the resistance to an unpainted, grounded surface on the frame at B+, B–, and all fuses.

A resistance reading of less than 1000ohms indicates a serious short to frame. If this condition exists, find the source of low resistance or short to frame using step 6. Do not continue until this condition is corrected.

3.Remove the battery from the truck. See “Battery” on page6-4.

4.Connect the battery lead to the truck.