For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
Schematic Reference: Fog Lights Schematics
1 | Did you perform the Lighting System Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Lighting Systems
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 16

Go to Step 19

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 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 7

Go to Step 18

7 | 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 8 | Go to Step 13
8 | Connect a 10-amp fused jumper wire between the switch side battery positive voltage circuit of the fog lamp relay and the front fog lamps supply voltage circuit of the fog lamp relay. Do the fog lamps illuminate? | Go to Step 17 | 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 21

Go to Step 22

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 26 | Go to Step 14
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 26 | Go to Step 15
13 | 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 26 | Go to Step 15
14 | 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 26 | Go to Step 23
15 | 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 26 | Go to Step 24
16 | 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 26 | Go to Step 19
17 | Inspect for poor connections at the fog lamp 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 26 | Go to Step 25
18 | Repair an open, high resistance, or short to ground in the coil side voltage supply circuit of the fog lamp relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 26 | --
19 | 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 26 | --
20 | 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 26 | --
21 | 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 26 | --
22 | 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 26 | --
23 | Replace the fog lamp switch. Refer to Fog Lamp Switch Replacement . Did you complete the replacement? | Go to Step 26 | --
24 | Important: Perform the set up procedure for the BCM. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | Go to Step 26 | --
25 | Replace the fog lamp relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement? | Go to Step 26 | --
26 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3