Diagnostic Instructions

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B2545 01: Backup Lamps Control Circuit Short to Battery

DTC B2545 02: Backup Lamps Control Circuit Short to Ground

DTC B2545 04: Backup Lamps Control Circuit Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Backup Lamps	B2545 02	B2545 04	B2545 01	--

Circuit/System Description

When the transmission is placed in reverse gear, the engine control module (ECM) 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 ECM via serial data requesting the BCM to remove battery voltage from the backup lamp control circuit.

Conditions for Running the DTC

Reverse Gear engaged

Conditions for Setting the DTC

B2545 01

The BCM detects a short to voltage on the control circuit.

B2545 02

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

B2545 04

The BCM detects an open control circuit.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, perform the Backup Lamps Relay Command test. The backup lamps should be ON / OFF

Circuit/System Testing

1. Ignition OFF, disconnect the appropriate harness connector at the appropriate tail lamp listed below:

•	E42L Tail lamp left

•	E42R Tail lamp right

2. Test for less than 5 Ω between the appropriate ground circuit harness connector terminal listed below and ground:

•	E42L Tail lamp left harness connector terminal B

•	E42R Tail lamp right harness connector terminal E

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

3. Connect a test lamp between the appropriate control circuit harness connector terminal listed below and ground :

•	E42L Tail lamp left harness connector terminal E

•	E42R Tail lamp right harness connector terminal F

4. Command the Backup Lamps Relay Command test 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 Body Control Module (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 Body Control Module (BCM).

5. If all circuits test normal, replace the appropriate backup lamp.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.