GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Headlights Schematics

1

Did you perform the Lighting Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify the fault is present.

Does the system operate normally?

Go to Testing for Electrical Intermittents in Wiring Systems

Go to Step 3

3

  1. Ensure the headlamp switch is in the AUTO position
  2. With the scan tool command the head lamp power relay ON.

Do the headlamps come on?

Go to Step 4

Go to Headlamps Inoperative in Low Light Conditions

4

With the scan tool, read the flash to pass switch status as you move the switch.

Does the scan tool display the switch status change?

Go to Step 10

Go to Step 5

5

Connect a test lamp (back probe) between the flash to pass battery feed circuit at the headlamp dimmer switch connector C201C and a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 7

6

  1. Connect a test lamp (back probe) between the flash to pass signal circuit at the headlamp dimmer switch connector C201 a good ground.
  2. While probing, move the flash to pass switch.

Does the test lamp illuminate?

Go to Step 8

Go to Step 9

7

Repair the flash to pass battery feed circuit open between the engine wiring harness junction block and the switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

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8

Repair the open in the flash to pass signal circuit between the switch and the BCM. Refer to Wiring Repairs in Wiring Systems. If no open is found, replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the repair?

Go to Step 11

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9

Replace the headlamp dimmer switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in steering wheel and column - tilt.

Did you complete the replacement?

Go to Step 11

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10

Replace BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 11

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11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3