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.

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.

Front fog lamp switch stuck.

The condition for setting the DTC is not longer present.

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

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool Front Fog Lamps Switch parameter. The reading should change between Active / Inactive when changing between pressed and released front fog lamp switch button.

1. Ignition OFF, disconnect the X1 and X3 harness connector at the K9 Body Control Module (BCM).
2. Ignition ON, test for less than 0.3  V at the K9 Body Control Module (BCM) signal circuit harness connector X1 terminal 9 and ground.

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

3. Test for less than 0.3  V at the K9 Body Control Module (BCM) 12 V reference circuit harness connector X3 terminal 4 and ground.

⇒	If greater than the specified value, test the 12 V reference circuit for a short to voltage.

4. Ignition OFF, test for infinite resistance between the K9 Body Control Module (BCM) signal circuit harness connector X1 terminal 9 and ground.

⇒	If lower than the specified value, test the signal circuit for a short to ground.

5. Test for infinite resistance between the K9 Body Control Module (BCM) 12 V reference circuit harness connector X3 terminal 4 and ground.

⇒	If lower than the specified value, test the 12 V reference circuit for a short to ground.

6. Press and hold the front fog lamp switch button.
7. Test for 100-200 Ω between the K9 Body Control Module (BCM) 12 V reference circuit harness connector X3 terminal 4 and the K9 Body Control Module (BCM) signal circuit harness connector X1 terminal 9.

⇒	If not within the specified range, test the 12 V reference circuit and the signal circuit for an open / high resistance. If the circuits test normal replace the S30 Headlamp Switch.

8. If all circuits test normal, replace the K9 Body Control Module (BCM).

Static Test

Ignition OFF, disconnect the harness connector at the S30 Headlamp Switch. Press and hold the front fog lamp switch button, test for 100-200 Ω at the S30 Headlamp Switch terminal 1 and terminal 12.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.