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

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

Do the fog lamps illuminate?

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

Go to Step 3

3

  1. Install a scan tool.
  2. Observe the Front Fog Lamp Switch parameter in the Instrument Panel Integration Module (IPM) Non-HVAC Data list.

Does the scan tool display ON?

Go to Step 6

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the headlamp switch.
  3. Connect a test lamp between the front fog lamp switch signal circuit and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 12

5

Connect a test lamp between the front fog lamp switch signal circuit and the ground circuit of the front fog lamp switch.

Does the test lamp illuminate?

Go to Step 17

Go to Step 18

6

  1. With a scan tool, select from the Dash Integration Module (DIM) Special Functions Output Controls, the Front Fog Lamps.
  2. With the scan tool, command the FOG LP relay ON and OFF.

Do you hear a click when you command the FOG LP relay ON and OFF?

Go to Step 9

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Remove the FOG LP relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ignition 1 voltage circuit of the FOG LP relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 19

8

  1. With the fog lamp switch in the ON position, connect a test lamp between the ignition 1 voltage circuit and the control circuit of the FOG LP relay coil.
  2. With a scan tool command the FOG LP relay ON.

Does the test lamp illuminate?

Go to Step 16

Go to Step 13

9

  1. Turn OFF the ignition.
  2. Remove the FOG LP relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the battery positive voltage circuit of the FOG LP relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 20

10

Connect a 15-amp fused jumper between the battery positive voltage circuit of the FOG LP relay switch and the supply voltage circuit of the fog lamps.

Do the fog lamps illuminate?

Go to Step 16

Go to Step 11

11

  1. Disconnect the harness connector of the fog lamp.
  2. Connect a test lamp between the supply voltage circuit of the fog lamp and a good ground.

Does the test lamp illuminate?

Go to Step 21

Go to Step 22

12

Test the 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 27

Go to Step 14

13

Test the control circuit of the FOG LP relay for an open or short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 15

14

Inspect for poor connections at the IPM. 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 27

Go to Step 24

15

Inspect for poor connections at the DIM. 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 27

Go to Step 23

16

Inspect for poor connections at the FOG LP 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 27

Go to Step 25

17

Inspect for poor connections at the headlamp 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 27

Go to Step 26

18

Repair an open or high resistance in the ground circuit of the fog lamp switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

19

Repair an open or high resistance in the ignition 1 voltage circuit of the FOG LP relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

20

Repair an open or high resistance in the battery positive voltage circuit of the FOG LP relay switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

21

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

Did you complete the repair?

Go to Step 27

--

22

Repair an open or high resistance in the supply voltage circuit of the fog lamps. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

--

23

Replace the DIM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 27

--

24

Replace the IPM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 27

--

25

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

Did you complete the replacement?

Go to Step 27

--

26

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Did you complete the replacement?

Go to Step 27

--

27

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2