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
--- | --- | --- | --- | ---
Front Fog Lamp Relay B+ | 1 | 1 | 1 | --
Front Fog Lamp Switch Signal | 2 | 2 | 2 | --
Front Fog Lamp Relay Control | B2530 02 | B2530 05 | B2530 05 | --
Front Fog Lamp Control | 1 | 1 | 1 | --
Front Fog Lamp Relay Ground | -- | 1 | 1 | --
Fog Lamp - LF Ground | -- | 1 | 1 | --
Fog Lamp - RF Ground | -- | 1 | 1 | --
Front Fog Lamp Switch Ground | -- | 2 | 2 | --
1. Front Fog Lamps Malfunction 2. Front Fog Lamp Switch Malfunction

### Circuit/System Description

When the front fog lamp switch is placed in the ON position, ground is applied through the front fog lamp switch signal circuit at G300 to the body control module (BCM). The BCM applies battery voltage through the front fog lamp relay control circuit to the coil side of the front fog lamp relay. Battery voltage is applied at all times from the FOG LAMP fuse to the switch side of the front fog lamp relay. When the relay coil is energized, the relay switch contacts close and allow battery voltage to be applied from the FOG LAMP fuse, through the relay switch contacts, to the front fog lamps. Ground for the front fog lamps is applied at all times at G101 for the left front fog lamp and G102 for the right front fog lamp. G102 also serves as ground for the coil side of the front fog lamp relay.

### 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 pressing and releasing 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 Front Fog Lamp Switch Malfunction.

⇒ | If the parameter changes between the commanded states, refer to Front Fog Lamps Malfunction.

### Circuit/System Testing

#### Front Fog Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the front fog lamp switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal A.

⇒ | 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 C 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 C and ground. 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 an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the front fog lamp switch.

#### Front Fog Lamps Malfunction

1. Ignition OFF, disconnect the front fog lamp relay.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 85 and ground.

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

3. Ignition OFF, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the front fog lamp relay.

5. Disconnect the harness connector at the Inoperative front 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 the harness connector at the inoperative front fog lamp.
8. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the front fog lamps illuminate.

⇒ | If the front fog lamps do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative front fog lamp.

9. Connect a test lamp between the control circuit terminal 86 and ground.
10. 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 open/high resistance. If the circuit tests normal, replace the BCM.

11. If all circuits test normal, test or replace the front fog lamp relay.

#### 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

• | Relay Replacement

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