GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Fog Lights Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn the ignition to the ON position.
  2. Turn the headlamp switch to the PARK position.
  3. Place the fog lamp switch in the ON position.

Are the fog lamps ON?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Is only one fog lamp inoperative?

Go to Step 4

Go to Step 6

4

  1. Disconnect the inoperative fog lamp.
  2. Using a test lamp connected to ground, probe the fog lamps supply voltage circuit of the inoperative fog lamp.

Does the test lamp illuminate?

Go to Step 5

Go to Step 23

5

Using a test lamp, probe between the ground circuit and supply voltage circuit of the inoperative fog lamp.

Does the test lamp illuminate?

Go to Step 19

Go to Step 24

6

  1. Place the headlamp switch in the HEAD position.
  2. Place the headlamp dimmer switch in the high beam position.

Do the high beam headlamps operate properly?

Go to Step 7

Go to Headlamps Inoperative - High Beams

7

Check the FOG LP fuse for an open.

Is the FOG LP fuse open?

Go to Step 17

Go to Step 8

8

  1. Disconnect the fog lamp relay.
  2. Turn the ignition to the ON position.
  3. Connect a test lamp between the switch side supply of the fog lamp relay and a ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 21

9

  1. Turn the headlamp switch to the PARK position.
  2. Place the headlamp dimmer switch in the low beam position.
  3. Connect a test lamp between the coil side supply of the fog lamp relay and a ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 21

10

  1. With the fog lamp switch in the ON position.
  2. Connect a test lamp between the coil side supply of the fog lamp relay and the control circuit of the fog lamp relay.

Does the test lamp illuminate?

Go to Step 12

Go to Step 11

11

  1. Disconnect the fog lamp switch connector.
  2. Connect a test lamp between the fog lamps enable circuit of the fog lamp switch and battery positive voltage.

Does the test lamp illuminate?

Go to Step 13

Go to Step 15

12

Connect a fused jumper between the switch side supply of the fog lamp relay and the fog lamps supply voltage circuit of the fog lamp relay.

Do the fog lamps illuminate?

Go to Step 20

Go to Step 16

13

  1. Connect a test lamp between the coil side supply of the fog lamp relay and the control circuit of the fog lamp relay.
  2. Connect a fused jumper between the fog lamps enable circuit and the fog lamp relay control circuit of the fog lamp switch.

Does the test lamp illuminate?

Go to Step 18

Go to Step 14

14

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

Did you find and correct the condition?

Go to Step 30

Go to Step 21

15

Test for an open, high resistance, or short to battery positive voltage in the fog lamps enable circuit of the fog lamp switch . Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 30

Go to Step 22

16

Test for a open or high resistance in the fog lamp supply voltage circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 30

Go to Step 21

17

Test for a short to ground in the fog lamp supply voltage circuit or the fog lamp indicator supply voltage circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 30

Go to Step 21

18

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 .

Did you find and correct the condition?

Go to Step 30

Go to Step 26

19

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 .

Did you find and correct the condition?

Go to Step 30

Go to Step 25

20

Inspect for poor connections at the harness connector of the fog lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 30

Go to Step 27

21

Inspect for poor connections at the harness connector of the fuse block - underhood. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 30

Go to Step 28

22

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 .

Did you find and correct the condition?

Go to Step 30

Go to Step 29

23

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

Has the repair been made?

Go to Step 30

--

24

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

Has the repair been made?

Go to Step 30

--

25

Replace the inoperative fog lamp. Refer to Front Fog Lamp Replacement .

Has the repair been made?

Go to Step 30

--

26

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

Has the repair been made?

Go to Step 30

--

27

Replace the fog lamp relay. Refer to Relay Replacement .

Has the repair been made?

Go to Step 30

--

28

Replace the fuse block - underhood. Refer to Underhood Electrical Center or Junction Block Replacement .

Has the repair been made?

Go to Step 30

--

29

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Has the repair been made?

Go to Step 30

--

30

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2