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 body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch resistor ladder to the BCM. The BCM interprets this voltage signal and will command the interior lights to the desired brightness, command the front fog lamps or the rear fog lamps depending upon the switch setting selected.
Reference Information
Schematic Reference
Fog Lights Schematics (Fog Lights Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Rear Fog Lamps Switch parameter. The parameter should change between Active and Inactive each time the rear fog lamp switch is pressed.
• If the value does not change, refer to Rear Fog Lamp Switch Malfunction
2. Command the Rear Fog Lamp(s) Relay ON and OFF with a scan tool. The rear fog lamp should turn ON and OFF when changing between the commanded states
• If the rear fog lamps are always ON or always OFF, refer to Rear Fog Lamp Malfunction
Circuit/System Testing
Rear Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition OFF, test for 0.4K ohm to 1 ohm between the signal circuit terminal 12 and ground.
• If greater than the specified value, test the low reference circuit for an short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
• If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.
3. Test for greater than 10V between the 12V reference circuit terminal 1 and ground.
• If less than the specified range, test the 12V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
4. If all circuits test normal, replace the K9 BCM.
Rear Fog Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the E5 fog lamp-rear.
2. Test for less than 30 ohm between the ground circuit terminal C and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal A and ground.
4. Ignition ON, command the Rear Fog Lamp(s) Relay 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 K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, replace the E5 fog lamp-rear.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Tail Lamp Replacement (Service and Repair)
* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming.