GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Fog Lights Schematics

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 front fog lamps are always on.

Do the front 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 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:

    • Headlamp Ambient Light Sensor
    • Park Brake Switch
    • Auto Headlamps
    • Headlamp Relay Feedback
    • Headlamp Power Relay
    • Front Fog Lamp Switch
    • Front Fog Lamp Relay
    • Park Lamp Relay

Did you find and correct a problem?

Go to Step 13

Go to Step 4

4

Use the scan tool to monitor the front fog lamp switch input with the switch in the OFF position.

Does the scan tool indicate that the switch is ON?

Go to Step 7

Go to Step 5

5

Remove the front fog lamp relay.

Do the front fog lamps turn OFF?

Go to Step 6

Go to Step 8

6

Using a J 39200 digital multimeter (DMM), check for continuity to ground the front fog lamp relay control circuit at the front fog lamp relay connector in the underhood fuse block. Refer to Electrical Center Identification Views and Circuit Testing in Wiring Systems.

Is continuity present?

Go to Step 9

Go to Step 11

7

  1. Disconnect the front fog lamp switch.
  2. Test the front fog lamp switch signal circuit for a short to ground. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 10

Go to Step 12

8

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

Did you complete the repair?

Go to Step 13

--

9

Repair the short to ground in the front fog lamp relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

10

Repair the short to ground in the front fog lamp switch signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the front fog lamp relay. Refer to Fog Lamp Relay Replacement .

Did you complete the repair?

Go to Step 13

--

12

Replace the front fog lamp switch. Refer to Headlamp Switch Replacement

Did you complete the repair?

Go to Step 13

--

13

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3