For 1990-2009 cars

### Diagnostic Instructions

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. 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 Signal | 1 | 1 | 2 | --
Right Front Fog Lamp Ground | -- | 3 | -- | --
Headlight Switch 12 V Reference | 1 | 1 | 1 | --
Headlight Switch Signal | 1 | 1 | 2 | --
Left Front Fog Lamp Ground | -- | 4 | -- | --
1. Front fog lamps inoperative 2. Front fog lamps always ON 3. Right front fog lamp inoperative 4. Left front fog lamp inoperative

### Circuit/System Description

The front fog lamp relay is supplied with battery voltage at all times. The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The body control module (BCM) energizes the front fog lamp relay by applying ground to the front fog lamp relay control circuit. When the front fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the front fog lamp fuse to the front fog lamp supply voltage circuit which illuminates the front fog lamps. With the front fog lamp switch activated the BCM sends a message via serial data to the instrument panel cluster (IPC) requesting the instrument panel cluster (IPC) to illuminate the front fog indicator.

### 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, perform the Front Fog Lamps Relay Command test. The front fog lamps should be ON / OFF.

• | Ignition ON, perform the instrument cluster All Indicators test ON and OFF test. The front fog indicator should be ON / OFF.

### Circuit/System Testing

#### Front Fog Lamp Malfunction

1. Ignition OFF, disconnect the appropriate harness connector at the front fog lamps listed below:

• | E29LF Fog Lamp - Left Front

• | E29RF Fog Lamp - Right Front

2. Test for less than 5 Ω between the appropriate front fog lamp ground circuit harness connector terminal 2 and ground.

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

3. Disconnect the KR46 Front Fog Lamp Relay.
4. Ignition ON, test for less than 0.3 V between the signal circuit terminal 87 and ground.

⇒ | If greater than the specified value, test the signal circuit for an short to voltage.

5. Ignition OFF, test for infinite resistance between the signal circuit terminal 87 ground.

⇒ | If less than the specified value, test the signal circuit for an short to ground.

6. Test for less than 5 Ω between the signal circuit terminal 87 and the appropriate front fog lamp connector terminal 1.

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

7. If all circuits test normal, replace the KR46 Front Fog Lamp Relay.

#### Front Fog Indicator Malfunction

1. Ignition ON, command the instrument cluster All Indicators test ON and OFF with the scan tool. The front fog indicator lamp should be ON / OFF when changing between the commanded states.

⇒ | If the front fog indicator stays always on or always off, replace the P16 Instrument Panel Cluster (IPC).

⇒ | If the front fog indicator is changing between ON and OFF, replace the K9 Body Control Module (BCM).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Front Fog Lamp Replacement

• | Control Module References for BCM or instrument panel cluster replacement, setup and programming.