GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Lighting Systems Connector End Views or Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Verify that the tail, marker and license lamps are always on.

Do the tail, marker and license lamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Remove the park lamp relay.

Do the park lamps turn OFF?

Go to Step 4

Go to Step 9

4

  1. Ensure that the headlamp switch is in the OFF position and there is sufficient light to the ambient light sensor.
  2. Test for a ground signal at the park lamp relay control circuit terminal in the body relay block. Refer to Circuit Testing .

Was a ground signal present?

Go to Step 5

Go to Step 10

5

Use the scan tool to check the body control module (BCM) park lamp switch input data.

Does the scan tool indicate a park lamps OFF request signal?

Go to Step 8

Go to Step 6

6

Test for a short to ground in the park lamp switch signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 7

7

Inspect for poor connections at the harness connector of the headlamp switch. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 11

8

Inspect for poor connections at the harness connector of the BCM. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 13

Go to Step 12

9

Repair the short to voltage in one of the following circuits. Refer to Wiring Repairs :

    • The park lamp supply voltage
    • The tail lamp supply voltage
    • The license lamp supply voltage
    • The marker lamp supply voltage

Did you complete the repair?

Go to Step 13

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10

Replace the park lamp relay. Refer to Relay Replacement .

Did you complete the repair?

Go to Step 13

--

11

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Did you complete the repair?

Go to Step 13

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12

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 13

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13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3