GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify that the headlamps are inoperative in low light conditions.

Do the headlamps operate normally?

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

Go to Step 3

3

Turn the headlamp switch to the HEAD position.

Do the headlamps operate normally?

Go to Step 4

Go to Headlamps Inoperative - Low Beams

4

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:

    â€¢ Headlamp ambient light sensor
    â€¢ Auto headlamps
    â€¢ Headlamp relay feedback
    â€¢ Daytime running lamps relay
    â€¢ Headlamp power relay
    â€¢ High beam switch
    â€¢ Flash-to-Pass switch

Did you find and correct a problem?

Go to Step 5

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5

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3