GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Fog Lights Schematics

Connector End View Reference: Lighting Systems Connector End Views or Computer/Integrating Systems Connector End Views in Computer/Integrating Systems

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 rear fog lamps are always on.

Do the rear fog lamps operate normally?

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

Go to Step 3

3

Use the scan tool to monitor the rear fog lamp switch input while depressing the switch several times.

Does the scan tool indicate that the switch is ACTIVE at all times?

Go to Step 4

Go to Step 5

4

Test for a short to ground in the rear fog lamp switch signal circuit.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

5

Test the rear fog lamp relay control circuit for a short to ground.

Did you find and correct the condition?

Go to Step 13

Go to Step 6

6

Remove the rear fog lamp relay.

Do the rear fog lamps turn OFF?

Go to Step 7

Go to Step 9

7

  1. Ensure that the rear fog lamp switch is in the OFF position.
  2. Test for a ground signal at the rear fog lamp relay control circuit terminal in the body relay block. Refer to Circuit Testing in Wiring Systems.

Was a ground signal found?

Go to Step 8

Go to Step 12

8

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

9

Repair the short to voltage in the rear fog lamp supply voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

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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 13

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11

Replace the rear fog lamp switch. Refer to Rear Fog Lamp Switch Replacement.

Did you complete the repair?

Go to Step 13

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12

Replace the rear fog lamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the repair?

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