For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn ON the ignition, with the engine OFF.
2. Place the headlamp switch in the headlamp ON 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

Go to Step 3

3 | Is only one lamp inoperative? | Go to Step 4 | Go to Step 6
4 | Test the front fog lamp supply voltage circuit of the inoperative lamp for an open or high resistance. Did you find and correct the condition? | Go to Step 22 | Go to Step 5
5 | Test the ground circuit of the inoperative lamp for an open or high resistance. Did you find and correct the condition? | Go to Step 22 | Go to Step 15
6 | With a scan tool, command the fog lamps ON. Do the fog lamps illuminate? | Go to Step 9 | Go to Step 7
7 |

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

Does the test lamp illuminate?

Go to Step 8

Go to Step 17

8 | Probe the fog lamp relay control circuit of the fog lamp relay with a test lamp that is connected to battery positive voltage. Does the test lamp illuminate? | Go to Step 16 | Go to Step 12
9 |

1. Disconnect the fog lamp switch.
2. Momentarily connect the 3-amp fused jumper with between the front fog lamp switch signal circuit of the switch and battery positive voltage.

Do the fog lamps illuminate?

Go to Step 10

Go to Step 11

10 | Test the ignition 1 voltage circuit of the fog lamp switch for an open, high resistance or short to ground. Did you find and correct the condition? | Go to Step 22 | Go to Step 13
11 | Test the fog lamp switch signal circuit for an open, high resistance or short to ground. Did you find and correct the condition? | Go to Step 22 | Go to Step 14
12 | Test the fog lamp relay control circuit for an open or high resistance. Did you find and correct the condition? | Go to Step 22 | Go to Step 14
13 | Inspect for poor connections at the harness connector of the fog lamp switch. Did you find and correct the condition? | Go to Step 22 | Go to Step 19
14 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Body Control Module Replacement . Did you find and correct the condition? | Go to Step 22 | Go to Step 20
15 | Inspect for poor connections at the harness connector of the inoperative fog lamp. Did you find and correct the condition? | Go to Step 22 | Go to Step 18
16 | Inspect for poor connections at the fog lamp relay. Did you find and correct the condition? | Go to Step 22 | Go to Step 21
17 | Repair an open, high resistance, or short to ground in the coil side voltage supply circuit of the fog lamp relay. Did you complete the repair? | Go to Step 22 | --
18 | Replace the bulb or lamp assembly. Did you complete the replacement? | Go to Step 22 | --
19 | Replace the fog lamp switch. Did you complete the replacement? | Go to Step 22 | --
20 | Replace the BCM. Refer to Body Control Module Replacement . Did you complete the replacement? | Go to Step 22 | --
21 | Replace the fog lamp relay. Did you complete the replacement? | Go to Step 22 | --
22 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3