Circuit Description
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 battery voltage to the rear fog lamp relay control circuit. When the rear fog lamp relay is energized, battery voltage is applied via the REAR FOG/ALDL TOP SW fuse to the rear fog lamp supply voltage circuit which illuminates the rear fog lamps.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2540 Rear Fog Lamps Control Circuit
DTC Symptom | DTC Symptom Descriptor |
|---|---|
02 | Short to Ground |
05 | Open or Short to Voltage |
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | DTC B2540 02 will set when the BCM detects a short to ground in the rear fog lamp relay control circuit. |
| • | DTC B2540 05 will set when the BCM detects an open or short to voltage in the rear fog lamp relay control circuit. |
Action Taken When the DTC Sets
| • | When DTC B2540 02 is present, the rear fog lamps will not operate when the park lamps are ON and the rear fog lamp switch is active. |
| • | When DTC B2540 05 is present, the rear fog lamps and/or the rear fog lamp indicator will be ON at all times or will not operate. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | You issue a scan tool CLEAR DTCs command. |
| • | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. |
Diagnostic Aids
Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Fog Lights Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Is DTC B2540 02 present? | Go to Step 3 | Go to Step 5 |
3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 7 |
4 | Locate and repair a short to ground in the rear fog lamp relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
5 |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 8 |
6 | Locate and repair an open or short to battery voltage in the rear fog lamp relay control circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 7 |
7 | Replace the rear fog lamp relay. Refer to Relay Replacement . Did you complete the replacement? | Go to Step 10 | -- |
8 | Inspect for poor connections at the C2 harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
9 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 10 | -- |
10 |
Does the DTC reset? | Go to Step 2 | System OK |
