GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Headlights 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

  1. Place the headlamp switch in the ON position.
  2. Change the dimmer switch position from the high to low beam positions several times.

Does the headlamp system operate normally?

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

Go to Step 3

3

Are both high and low beam headlamps inoperative?

Go to Step 4

Refer to Headlamps Inoperative - Low Beams or Headlamps Inoperative - High Beams

4

With a scan tool, observe the Headlamp Switch parameter.

Does the scan tool indicate ACTIVE?

Go to Step 7

Go to Step 5

5

Connect a test lamp between the ground circuit of the headlamp switch connector and battery positive voltage.

Does the test lamp illuminate?

Go to Step 6

Go to Step 9

6

Test the headlamps switch headlamps ON signal circuit of the headlamp switch the following:

    • A high resistance
    • An open
    • A short to ground

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

7

Inspect for poor connections to the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

8

Inspect for poor connections to the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9

Repair the ground circuit of the headlamp switch. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 12

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10

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 12

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11

Replace the headlamp switch. Refer to Headlamp Switch Replacement

Did you complete the replacement?

Go to Step 12

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12

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3