B2545

DTC B2545

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.

DTC Descriptors
DTC B2545 02
- Backup Lamps Circuit Short to Ground

DTC B2545 04
- Backup Lamps Circuit Open

Diagnostic Fault Information





Circuit/System Description

When the engine is running and the transmission is placed in reverse gear, the transmission control module (TCM) sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position. The BCM applies battery voltage to the backup lamps. The backup lamps are permanently grounded. Once the driver moves the gear selector out of the reverse position, a message is sent by the TCM via serial data requesting the BCM to remove battery voltage from the backup lamp signal circuit. The BCM will not apply battery voltage to the backup lamps if the engine is not running.

Conditions for Running the DTC

Reverse Gear engaged.

Conditions for Setting the DTC

B2545 02

The BCM detects a short to ground on the backup lamps control circuit.

B2545 04

The BCM detects an open on the backup lamps control circuit.

Action Taken When the DTC Sets

The appropriate backup lamp is inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
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

Ignition ON, command the Backup Lamps Relay Command ON and OFF with a scan tool. The backup lamps should turn ON and OFF when changing between the commanded states.

Circuit/System Testing

Note: If DTC B2545 or B3950 are set fuse block underhood BCM fuse 32 may be open. Test circuit and fuse before replacing BCM.

1. Ignition OFF, disconnect the harness connector at the appropriate E42 tail lamp.
2. Test for less than 5 ohm between the ground circuit terminal C and ground.

• If greater than the specified value, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal D and ground.
4. Command the Backup Lamps Relay Command 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 circuits test normal, replace the K9 BCM.

5. If all circuits test normal, replace the tail lamp.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Tail Lamp Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming