Backup Lamps Malfunction

Backup Lamps Malfunction

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview





Circuit/System Description

When the PRNDL is placed in the REVERSE position, a GMLAN signal is sent from the transmission control module (TCM) to the body control module (BCM). The BCM then applies voltage through the backup lamps voltage supply circuit to the LED driver module. The LED drive module then illuminates the backup lamps.

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 1.0 ohm of resistance between the ground circuit terminal C for Domestic or H for Export 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 E and the ground circuit terminal C or H.
4. Ignition ON, place the PRNDL in the reverse position. 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 body control module.

• 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 body control module.

5. If all circuits test normal, test or replace the appropriate component.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Tail Lamp Replacement (Impala) Tail Lamp Replacement (Monte Carlo)
* Rearview Mirror Replacement
* Control Module References for BCM replacement, setup, and programming Programming and Relearning Verification Tests