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.

Circuit/System Description

The CHMSL BACKUP fuse in the instrument panel (I/P) fuse block supplies battery positive voltage to the body control module (BCM). When the driver places the gear selection into the REVERSE position, the powertrain control module (PCM) sends a class 2 message to the BCM. The message indicates that the gear selector lever is in the REVERSE position. The BCM then applies voltage to the backup lamp supply voltage circuit. Ground for the left backup lamps is from G401 and for the right backup lamp is from G400.

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

1. Place the gear selector in PARK or neutral.
2. Ignition ON, observer the backup lamps. The backup lamps should not be illuminated.

• If the backup lamps are illuminated, Refer to Backup Lamps Always On

3. Refer to Backup Lamps Inoperative

Circuit/System Testing
Backup Lamps Always On

Test the backup lamp supply voltage circuit for a short to voltage. If circuit tests normal, replace the BCM.

Backup Lamps Inoperative
1. Ignition OFF, disconnect the X1 harness connector at the BCM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 52 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Test the backup lamp supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

Repair Instructions

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

Control Module References (Programming and Relearning)