Backup Lamps Malfunction

Backup Lamps Malfunction

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

Diagnostic Fault Information






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 tail lamp assemblies illuminating 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 5.0 ohms of resistance between the ground circuit listed below and ground.
^ Pontiac - terminal GRND
^ All others - terminal B
^ If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the supply voltage circuit listed below and the ground circuit.
^ Pontiac - terminal Major
^ All others - terminal A

4. Ignition ON, cycle the PRNDL between the PARK and REVERSE positions. The test lamp should turn ON and OFF when changing between park and reverse.
^ If the test lamp is always ON, test the supply voltage 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 supply voltage 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
Perform the [Diagnostic Repair Verification - Vehicle Diagnostic Information] after completing the diagnostic procedure. Diagnostic Repair Verification - Vehicle Diagnostic Information
^ [Control Module References] for BCM replacement, setup, and programming Programming and Relearning
^ [Tail Lamp Replacement]