Backup Lamps Malfunction

Backup Lamps Malfunction

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.

Diagnostic Fault Information






Circuit/System Description

When the PRNDL is placed in the REVERSE position, a serial data signal is sent from the transmission control module (TCM) to the body control module (BCM). The BCM then applies voltage through the backup lamps control circuit to the tail lamp assemblies illuminating the backup lamps. The engine may need to be running for the backup lamps to function.

Reference Information

Schematic Reference

Exterior Lights Schematics Exterior Lights Schematics

Connector End View Reference

Component Connector End Views A/C Compressor Clutch

Description and Operation

Exterior Lighting Systems Description and Operation Exterior Lighting Systems

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 Control Module References for scan tool information

Circuit/System Verification

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

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the backup lamp.

2. Test for less than 5 ohms between the following ground circuit terminal listed below and ground:

* RPO Z88 - terminal 1

* RPO WDA - terminal 2

* RPO W49/X88 - terminal B

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

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

* RPO Z88 - terminal 2

* RPO WDA - terminal 1

* RPO W49/X88 - terminal A

4. Command the Backup Lamps 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 BCM.

• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

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

Repair Instructions

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

* Tail Lamp Replacement (Traverse) Service and RepairTail Lamp Replacement (Acadia) Service and RepairTail Lamp Replacement (Enclave) Service and Repair

* Backup Lamp Bulb Replacement (Traverse) Service and RepairBackup Lamp Bulb Replacement (Acadia) Service and RepairBackup Lamp Bulb Replacement (Enclave) Service and Repair

* Control Module References Control Module References for BCM replacement, programming and setup