GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Lighting Systems?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn the ignition on.
  2. Move the headlamp switch to the headlamp position.
  3. Turn the foglamp switch on.

Do both fog lamps operate?

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

Go to Step 3

3

Is only one lamp inoperative?

Go to Step 4

Go to Step 5

4

  1. Inspect the power supply or ground circuit for a poor connection or an open in the inoperative lamp. Refer to Circuit Testing in Wiring Systems.
  2. Repair the poor connection or open in the inoperative lamp. Refer to Wiring Repairs in Wiring Systems.
  3. If no fault is found, replace the inoperative lamp.

Did you complete the repair?

System OK

--

5

Inspect the FOG fuse for an open.

Is the fuse open?

Go to Step 6

Go to Step 8

6

Test the battery supply circuit of the fog lamp relay for a short to ground. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

System OK

Go to Step 7

7

Repair a short to ground in the foglamp feed circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

System OK

--

8

Test the battery supply circuit of the fog lamp relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

System OK

Go to Step 9

9

  1. Remove the fog lamp relay.
  2. Install a fused jumper wire across the foglamp relay switch terminals in the Fuse Block.

Do the fog lamps operate?

Go to Step 10

Go to Step 16

10

  1. Disconnect the foglamp switch.
  2. Test the fog lamp switch for continuity across the switch contacts with the button depressed.

Is continuity present across the switch contacts with the button depressed?

Go to Step 12

Go to Step 11

11

Replace the fog lamp switch. Refer to Fog Lamp Switch Replacement in Lighting.

Is repair complete?

System OK

--

12

Test the parklamp feed circuit for an open or short to ground between the headlamp switch and the fog lamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

System OK

Go to Step 13

13

Test the fog lamp switch signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

System OK

Go to Step 14

14

Test the fog lamp relay ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

System OK

Go to Step 15

15

Replace the fog lamp relay.

Is repair complete?

System OK

--

16

Test the fog lamp feed circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

System OK

Go to Step 17

17

Repair the open in the foglamp ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

System OK

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