GM Service Manual Online
For 1990-2009 cars only

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Schematic Reference: Fog Lights Schematics

Connector End View Reference: Master Electrical Component List in Wiring 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

  1. Turn ON the ignition, with the engine OFF.
  2. Place the headlamp switch in the HEADLAMP position.
  3. Place the fog lamp switch in the ON position.

Do both fog lamps illuminate?

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. Disconnect the inoperative fog lamp.
  2. Probe the front fog lamps supply voltage circuit with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 18

Go to Step 20

5

With a scan tool, command the fog lamps ON.

Do the fog lamps illuminate?

Go to Step 10

Go to Step 6

6

  1. Disconnect the fog lamps relay.
  2. Probe the coil side battery positive voltage circuit of the fog lamps relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 13

7

Probe the fog lamp relay control circuit of the fog lamps relay with a test lamp that is connected to battery positive voltage.

Does the test lamp illuminate?

Go to Step 8

Go to Step 14

8

Connect a 10-amp fused jumper wire between the switch side battery positive voltage circuit of the fog lamps relay and the front fog lamps supply voltage circuit of the fog lamps relay.

Do the fog lamps illuminate?

Go to Step 19

Go to Step 9

9

  1. Leave the fused jumper wire connected.
  2. Disconnect one of the fog lamps.
  3. Probe the front fog lamps supply voltage circuit of the disconnected fog lamp with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 22

Go to Step 23

10

  1. Disconnect the fog lamp switch.
  2. Connect a 3-amp fused jumper wire between the front fog lamp switch signal circuit and a good ground.

Do the fog lamps illuminate?

Go to Step 11

Go to Step 12

11

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

Did you find and correct the condition?

Go to Step 28

Go to Step 15

12

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

Did you find and correct the condition?

Go to Step 28

Go to Step 16

13

Test the front fog lamps supply voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 28

Go to Step 17

14

Test the fog lamp relay control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 28

Go to Step 16

15

Inspect for poor connections at the harness connector of the fog lamp 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 28

Go to Step 24

16

Inspect for poor connections at the harness connector of 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 28

Go to Step 25

17

Inspect for poor connections at the harness connector of the RH instrument panel (I/P) junction block. 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 28

Go to Step 26

18

Inspect for poor connections at the harness connector of the inoperative fog lamp. 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 28

Go to Step 20

19

Inspect for poor connections at the fog lamps relay. 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 28

Go to Step 27

20

Repair an open or high resistance in the front fog lamp supply voltage circuit of the inoperative fog lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

21

Repair an open or high resistance in the ground circuit of the inoperative fog lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

22

Repair an open or high resistance in the ground circuit of the front fog lamps. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

23

Repair an open or high resistance in the front fog lamps supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 28

--

24

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

Did you complete the replacement?

Go to Step 28

--

25

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 28

--

26

Replace the RH I/P junction block. Refer to Instrument Panel Electrical Center or Junction Block Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 28

--

27

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

Did you complete the replacement?

Go to Step 28

--

28

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3