• 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.

The front fog lamp relay is supplied with battery voltage at all times. The front fog lamp switch signal circuit is grounded through a resistor momentarily when the front fog lamp switch is pressed. 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 contacts close and battery voltage is applied through the front fog lamp fuse to the front fog lamp control circuit which illuminates the front fog lamps.

• Battery voltage must be between 9-16 V.
• Front fog lamps ON.

The BCM detects a short to voltage in the front fog lamp relay control circuit for 5 s or greater.

The BCM detects a short to ground in the front fog lamp relay control circuit.

The BCM detects an open in the front fog lamp relay control circuit.

The front fog lamps will not operate when the park lamps are ON and the front fog lamp switch is active.

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Fog Lights Schematics

Master Electrical Component List

Exterior Lighting Systems Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
2. Connect a 3 A fused jumper between the control circuit terminal 10 and ground, ignition ON.
3. Verify a test lamp illuminates between the front fog lamp fuse (F39UA) and ground.
• If the test lamp does not illuminate
1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block – Underhood.
2. Test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the X50A Fuse Block – Underhood.
• If the test lamp illuminates
4. Ignition OFF, remove the fused jumper wire
5. Ignition ON, verify the test lamp does not illuminate between the front fog lamp fuse (F39UA) and ground
• If the test lamp illuminates
1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block – Underhood.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the X50A Fuse Block – Underhood
• If the test lamp does not illuminate
6. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block – Underhood.
7. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V.
8. Replace the K9 Body Control Module.

Perform the Diagnostic Repair Verification after completing the repair.

• Engine Wiring Harness Junction Block Replacement
• Control Module References for BCM replacement, programming, and setup