For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Fog Lamp Relay B+ | 1 | 1 | -- | --
Fog Lamp Switch Signal | 2 | 2 | 2 | --
Fog Lamp Relay Control | 1 | 1 | B2530 00 | --
Fog Lamp Control | 1 | 1 | 1 | --
Fog Lamp - LF Ground | -- | 1 | -- | --
Fog Lamp - RF Ground | -- | 1 | -- | --
Fog Lamp Switch Ground | -- | 2 | -- | --
1. Fog Lamps Malfunction 2. Fog Lamp Switch Malfunction

### Circuit/System Description

The fog lamp relay is supplied with battery voltage at all times. The fog lamp switch signal circuit is grounded momentarily by pressing the fog lamp switch. The body control module (BCM) energizes the fog lamp relay by applying ground to the fog lamp relay control circuit. When the fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FOG LAMP fuse to the fog lamp supply voltage circuit which illuminates the fog lamps.

### Reference Information

#### Schematic Reference

Fog Lights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior Lighting Systems Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Ignition ON, observe the scan tool Front Fog Lamp Switch parameter while activating the front fog lamp switch. The parameter should change between Active and Inactive.

⇒ | If the parameter does not change between the commanded states, refer to Fog Lamp Switch Malfunction.

### Circuit/System Testing

#### Fog Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the rear window wiper/washer/fog lamp switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 5.

⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Front Fog Lamp Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 4 and the ground circuit terminal 5. Verify the scan tool Front Fog Lamp Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the rear window wiper/washer/fog lamp switch.

#### Fog Lamps Malfunction

1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal 19 and ground.
3. Command the Front Fog Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

4. Ignition OFF, connect the X2 harness connector at the underhood fuse block.
5. Disconnect the harness connector at the inoperative fog lamp.
6. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect a test lamp between the control circuit terminal A and ground.
8. Command the Front Fog Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the underhood fuse block.

⇒ | If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block.

⇒ | If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.

9. If all circuits test normal, replace the inoperative fog lamp.

#### Front Fog Lamp Indicator Malfunction

Ignition ON, with a scan tool perform the Display Test for the instrument panel cluster (IPC) and observe the front fog lamp indicator.

⇒ | If the front fog lamp indicator illuminates during the test, replace the BCM.

⇒ | If the front fog lamp indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Fog Lamp Switch Replacement

• | Front Fog Lamp Replacement

• | Underhood Electrical Center or Junction Block Replacement

• | Control Module References for BCM or IPC replacement, setup, and programming