• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

With the engine running and the transmission in the reverse position, the transmission control module (TCM) sends a serial data message to the body control module (BCM). The message indicates that the gear selector is in the reverse position. The BCM applies battery voltage to the backup lamps control circuit illuminating the backup lamps. Once the driver moves the gear selector out of the reverse position, a message is sent by the TCM via serial data requesting the BCM to remove battery voltage from the backup lamps control circuit. The engine must be running for the backup lamps to operate.

• Battery voltage must be between 9-16 V.
• Engine RUNNING.
• Transmission placed in REVERSE gear.

The BCM detects an open/high resistance in the backup lamps control circuit.

The BCM detects a short to ground in the backup lamps control circuit.

The backup lamps will not operate.

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Exterior Lights Schematics

Master Electrical Component List

Exterior Lighting Systems Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E5 Backup Lamp.
2. Test for less than 5 Ω between the ground circuit at the socket terminal and ground.
• If 5 Ω or greater
1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, repair the open/high resistance in the ground connection.
• If less than 5 Ω
3. Connect a test lamp between the control circuit at the socket terminal and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the Backup Lamps ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω
2. Ignition OFF, disconnect the X7 harness connector at the K9 Body Control Module and all other components associated with the control circuit.
3. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 Body Control Module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X7 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF
5. Test or replace the appropriate E5 Backup Lamp.

Perform the Diagnostic Repair Verification after completing the repair.

• Backup Bulb Replacement
• Control Module References for BCM replacement, programming, and setup