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 Body Control Module (BCM) receives a class 2 message from the Powertrain Control Module (PCM) requesting to illuminate the backup lamps, battery voltage is sent directly from the BCM through the backup lamp supply voltage circuit to the backup lamps.

Reference Information
Schematic Reference

Exterior Lights Schematics (Wiring Diagram Index)
Connector End View Reference

Component Connector End Views (Component Connector End 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 (Control Module References)for Scan Tool Information

Circuit/System Verification

Ignition ON, shift the vehicle in and out of reverse. The backup lamps should turn on and off.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at an affected backup lamp.
2. Test for less than 1 ohm of resistance between the ground circuit terminal A and ground.

• 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 B and ground circuit terminal.
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 affected backup lamps.

Repair Instructions

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

* Tail Lamp Assembly and /or Backup, Sidemarker, Stop, Turn Signal Bulb Replacement (Service and Repair)
* Control Module References (Control Module References)for BCM replacement, programming, and setup.