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 Lamps Control Circuit Short to GroundDTC B2540 05: Rear Fog Lamps 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 Switch Signal | B3588 00 | 2 | 2 | -- |
Rear Fog Lamp Relay Control | B2540 02 | B2540 05 | B2540 05 | -- |
Rear Fog Lamp control | 1 | 1 | 1 | -- |
Fog Lamp - LR Ground | -- | 1 | -- | -- |
Fog Lamp - RR Ground | -- | 1 | -- | -- |
Rear Fog Lamp Switch Ground | -- | 2 | -- | -- |
1. Rear Fog Lamps Malfunction 2. Rear Fog Lamp Switch Malfunction | ||||
Circuit/System Description
The rear fog lamp relay is supplied with battery voltage at all times from the REAR FOG fuse located in the rear fuse block. The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch. The body control module (BCM) energizes the rear fog lamp relay by applying ground to the rear fog lamp relay control circuit. When the rear fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the REAR FOG fuse to the rear fog lamp supply voltage circuit which illuminates the rear fog lamps.
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
DTC B2540 02
The BCM detects a short to ground in the rear fog lamp relay control circuit.
DTC B2540 05
The BCM detects a short to voltage or an open/high resistance in the rear fog lamp relay control circuit.
Actions Taken When the DTC Sets
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 rear fog lamp relay.
- Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
- Command the Rear Fog Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the rear fog lamp relay.
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
