Diagnostic Instructions
| • | 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. |
DTC Descriptors
DTC B2540 02: Rear Fog Lamp Control Circuit Short to GroundDTC B2540 05: Rear Fog Lamp Control Circuit Short to Battery or Open
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Rear Fog Lamp Relay Control | B2540 02 | B2540 05 | B2540 05 | -- |
Rear Fog Lamp Switch Signal | B3588 02 | -- | -- | -- |
Rear Fog Lamp Control | 1 | 1 | -- | -- |
Headlamp Switch Ground | -- | 1 | -- | -- |
Rear Fog Lamp Ground | -- | 1 | -- | -- |
1. Rear Fog Lamps Malfunction | ||||
Circuit/System Description
When the rear fog lamp switch is placed in the ON position, ground is applied to the auxiliary body control module (XBCM) through the rear fog lamp switch circuit. The XBCM then applies voltage to the rear fog lamp control circuit to the rear fog lamp.
Conditions for Running the DTC
| • | Battery voltage must be between 9-16 volts. |
| • | Rear fog lamps ON. |
Conditions for Setting the DTC
B2540 02
DTC B2540 02 will set when the BCM detects a short to ground in the rear fog lamp switch signal circuit.
B2540 05
DTC B2540 05 will set when the BCM detects a short to voltage or an open/high resistance in the rear fog lamp switch signal circuit.
Action Taken When the DTC Sets
When DTC B2540 is present, the rear fog lamps will not operate when the park lamps are ON and the rear fog lamp switch is active.
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the headlamp switch.
- Verify that a test lamp illuminates between B+ and the ground circuit terminal 8.
- Ignition ON, verify the scan tool Rear Fog Lamp Switch parameter is INACTIVE.
- Install a 3A fused jumper wire between the signal circuit terminal 6 and ground. Verify the scan tool Rear Fog Lamp Switch parameter is ACTIVE.
- If all circuits test normal, test or replace the headlamp switch.
| ⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance. |
| ⇒ | If not the specified value, test the signal circuit terminal 6 for a short to ground. If the circuit tests normal, replace the XBCM. |
| ⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the XBCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for XBCM replacement, setup, and programming |
