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 signal is sent to the body control module (BCM). The BCM then applies voltage through the backup lamps relay control circuit to the BACK/UP lamp relay in the underhood fuse block, and the inside rearview mirror. The BACK/UP lamp relay then illuminates the backup lamps.


Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
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 (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

Programming and Relearning (Programming and Relearning)for scan tool information


Circuit/System Verification

1. Connect a test lamp between the relay side of the backup lamp fuse and ground.
2. Ignition ON, verify that the test lamp turns on and off while commanding the backup lamps on and off with a scan tool.

• If the test lamp does not turn on and off while changing between the commanded states, refer to Backup Lamp Relay Control Circuit Test.

3. If 1 or both of the backup lamps do not turn on and off, refer to Backup Lamp Circuit Test.



Circuit/System Testing


Backup Lamp Relay Control Circuit Test
1. Ignition OFF, disconnect the X5 harness connector at the BCM.
2. Ignition ON, vehicle in park, verify the backup lamps are not on.

• If the backup lamps are on, test the backup lamp relay control circuit terminal 22 for a short to voltage. If the circuit tests normal replace the underhood fuse block.

3. Install a 10A fused jumper wire between the relay control circuit terminal 22 and battery voltage. Verify the backup lamps are on.

• If the backup lamps are not on, test the backup lamp relay control circuit for an open/high resistance or short to ground. If the circuit tests normal replace the underhood fuse block.

4. If all circuits test normal, replace the BCM.



Backup Lamp Circuit Test
1. Ignition OFF, disconnect the harness connector at the affected backup lamp.
2. Verify that a test lamp illuminates between the ground circuit terminal G 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 A and the ground circuit terminal G.
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 underhood fuse block.


• 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 underhood fuse block.

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



Repair Instructions

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

* Tail/Turn Signal Lamp Replacement (SUT) (Tail/Turn Signal Lamp Replacement (SUT))Tail/Turn Signal Lamp Replacement (SUV) (Tail/Turn Signal Lamp Replacement (SUV))
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Programming and Relearning (Programming and Relearning)for BCM replacement, programming, and setup