Rear Fog Lamps Malfunction
Rear Fog Lamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch. The body control module (BCM) responds to the rear fog lamp request by applying voltage to the rear fog lamps control circuit which illuminates the rear fog lamps.
Reference Information
Schematic Reference
Fog Lights Schematics Fog Lights Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, eclampsia ON.
2. Verify the scan tool Rear Fog Lamp Switch parameter changes between Active and Inactive while commanding the rear fog lamp ON and OFF with the rear fog lamp switch.
• If the parameter does not change
Refer to Rear Fog Lamp Switch Malfunction.
• If the parameter changes
3. Verify the rear fog lamps turn ON and OFF when commanding the Rear Fog Lamp ON and OFF with a scan tool.
• If the rear fog lamps do not turn ON and OFF
Refer to Rear Fog Lamp Malfunction.
• If the rear fog lamps turn ON and OFF
4. Verify the rear fog lamp indicator on the headlamp switch turns ON and OFF while commanding the rear fog lamp ON and OFF with the rear fog lamp switch.
• If the rear fog lamp indicator does not turn ON and OFF
Refer to Rear Fog Lamp Indicator Malfunction.
• If the rear fog lamp indicator turns ON and OFF
5. All OK.
Circuit/System Testing
Rear Fog Lamp Switch Malfunction
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S30 headlamp switch, ignition ON.
2. Test for B+ between the B+ circuit terminal 1 and ground.
• If less than B+
1. Ignition OFF, disconnect the X3 harness connector at the K9 body control module.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If B+
3. Verify the scan tool LED Backlight Dimming Command parameter is greater than 40%.
• If 40% or less
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 12 and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If greater than 40%
4. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the B+ circuit terminal 1.
5. Verify the scan tool LED Backlight Dimming Command parameter is less than 30%.
• If 30% or greater
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If less than 30%
6. Test or replace the S30 headlamp switch.
Rear Fog Lamps Malfunction
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate component listed below.
* E29LR fog lamp - left rear with CZ2
* E42LR tail lamp assembly - left without CZ2
* E42RR tail lamp assembly - right without CZ2
2. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.
* E29LR fog lamp - left rear terminal 2
* E42LR tail lamp assembly - left terminal 1
* E42RR tail lamp assembly - right terminal 1
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
* E29LR fog lamp - left rear terminal 1
* E42LR tail lamp assembly - left terminal 5
* E42RR tail lamp assembly - right terminal 7
4. Verify the test lamp turns ON and OFF when commanding the Rear Fog Lamps ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X5 harness connector at the K9 body control module.
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
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X5 harness connector at the K9 body control module, ignition ON.
2. 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, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the appropriate E29 fog lamp - rear.
Rear Fog Lamp Indicator Malfunction
1. Ignition OFF, all doors closed, all accessories OFF, disconnect the harness connector at the S30 headlamp switch. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 15 ohms between the ground circuit terminal 6 and ground.
• If 15 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 15 ohms
3. Connect a test lamp between the control circuit terminal 2 and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the Rear Fog Lamps ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X5 harness connector at the K9 body control module.
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
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X5 harness connector at the K9 body control module, ignition ON.
2. 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, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the S30 headlamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Tail Lamp Bulb Replacement Service and Repair
* Tail Lamp Replacement - Outboard Tail Lamp Replacement - Outboard
* Headlamp, Instrument Panel Lamp Dimmer, and Fog Lamp Switch Replacement Service and Repair
* Control Module References Control Module References for BCM replacement, programming, and setup