Backup Lamps Malfunction

Backup Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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.

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 (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, place the PRNDL in the REVERSE position. The backup lamps should illuminate.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate tail lamp assembly.
2. Test for less than 5.0 ohm between the ground circuit listed below and ground.

* RPO WDA - Terminal 2
* RPO Z88 - Terminal 1
* RPO W49 - 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 listed below and the ground circuit.

* RPO WDA - Terminal 1
* RPO Z88 - Terminal 2
* RPO W49 - Terminal A

4. Ignition ON, cycle the PRNDL between the PARK and REVERSE positions. The test lamp should turn ON and OFF when changing between park and reverse.

• 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 bulb.

Repair Instructions

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

* Backup Lamp Bulb Replacement (Acadia) (Service and Repair)Backup Lamp Bulb Replacement (Enclave) (Service and Repair)Backup Lamp Bulb Replacement (OUTLOOK) (Service and Repair)Backup Lamp Bulb Replacement (Traverse) (Service and Repair)
* Tail Lamp Replacement (Traverse) (Service and Repair)Tail Lamp Replacement (Acadia) (Service and Repair)Tail Lamp Replacement (Enclave) (Service and Repair)Tail Lamp Replacement (OUTLOOK) (Service and Repair)
* Inside Rearview Mirror Replacement (Inside Rearview Mirror Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming