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. Turn ON the low beam headlamps.
  3. Turn ON the rear fog lamps.

Do the rear fog lamps operate properly?

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

Go to Step 3

3

Are both rear fog lamps inoperative?

Go to Step 4

Go to Step 19

4

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn ON the low beam headlamps.
  4. With a scan tool, observe the Rear Fog Lamp Switch parameter in the body control module (BCM) lighting data list.
  5. Turn the rear fog lamp switch ON and OFF.

Does the scan tool indicate the rear fog lamp switch parameter changes from Active to Inactive as the switch is cycled?

Go to Step 5

Go to Step 9

5

  1. Turn the rear fog lamp switch to the ON position.
  2. With a scan tool, observe the Rear Fog Lamp Relay Cmd. in the BCM lighting data list.

Does the scan tool indicate the rear fog lamp relay Cmd. parameter is ON?

Go to Step 6

Go to Step 12

6

  1. Turn OFF the ignition.
  2. Disconnect the FOG RR relay. Refer to Relay Replacement in Wiring Systems.
  3. Connect a 15-amp fused jumper between the FOG RR relay switched voltage supply circuit and the rear fog lamp voltage supply circuit.
  4. Turn ON the ignition, with the engine OFF.

Do the rear fog lamps illuminate?

Go to Step 7

Go to Step 15

7

  1. Connect a test lamp between the rear fog lamp relay control circuit and the FOG RR relay voltage supply circuit.
  2. Turn ON the ignition, with the engine OFF.
  3. Place the rear fog lamp switch in the ON position.

Does the test lamp illuminate?

Go to Step 14

Go to Step 8

8

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

Did you find and correct the condition?

Go to Step 25

Go to Step 12

9

  1. Turn OFF the ignition.
  2. Disconnect the turn signal/multifunction switch.
  3. Connect a 3-amp fused jumper between the rear fog lamp switch signal circuit and the rear fog lamp switch ground circuit.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool observe the Rear Fog Lamp Switch parameter.

Does the scan tool display Active?

Go to Step 13

Go to Step 10

10

Locate and repair an open or high resistance in the rear fog lamp switch ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 11

11

Locate and repair an open, high resistance, or short to voltage in the rear fog lamp switch signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 12

12

Inspect for poor connections at the harness connector of the 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 25

Go to Step 21

13

Inspect for poor connections at the harness connector of the turn signal/multifunction 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 25

Go to Step 22

14

Inspect for poor connections at the FOG RR 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 25

Go to Step 24

15

Test the rear fog lamp voltage supply circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 16

16

Test the rear fog lamp ground 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 25

Go to Step 17

17

Test the FOG RR relay voltage supply 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 25

Go to Step 18

18

Inspect for poor connections at the instrument panel (I/P) relay 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 25

Go to Step 23

19

Test the rear fog lamp voltage supply circuit of the inoperative fog lamp for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 20

20

Test the rear fog lamp ground circuit of the inoperative fog lamp 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 25

--

21

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 25

--

22

Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 25

--

23

Replace the I/P relay block.

Did you complete the replacement?

Go to Step 25

--

24

Replace the FOG RR relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 25

--

25

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2