GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference: Lighting Systems Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Verify that the low and/or high beam headlamps are always on.

Do the headlamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Use the scan tool to inspect for the following related Body Control Module (BCM) Data/ Input Parameters and Output Controls. Refer to Scan Tool Data List for typical values and definitions:

    • Headlamp Ambient Light Sensor
    • Park Brake Switch
    • Auto Headlamps
    • Headlamp Relay Feedback
    • Daytime Running Lamps Relay
    • Headlamp Power Relay
    • Left Turn Signal
    • Right Turn Signal
    • High Beam Switch
    • Flash to Pass Switch

Did you find and correct a condition?

Go to Step 9

Go to Step 4

4

Remove the daytime running lamps (DRL) relay from the underhood fuse block.

Do the low and/or high beam headlamps remain on?

Go to Step 7

Go to Step 5

5

  1. Make sure the ignition switch is in the OFF position.
  2. Remove the headlamp grounding relay in the body relay block.
  3. Disconnect the BCM connector C1.
  4. Using the J 39200 digital multimeter (DMM), check for continuity to ground in the DRL relay control circuit. Refer to Circuit Testing in Wiring Systems.

Is continuity present?

Go to Step 6

Go to Step 8

6

Repair the short to ground in the DRL relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 9

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7

Repair the short to ground in the left headlamp high beam supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 9

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8

Replace the DRL relay. Refer to Relay Replacement

Did you complete the repair?

Go to Step 9

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9

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3