When the PRNDL is placed in the REVERSE position, a serial data signal is sent from the transmission control module (TCM) to the body control module (BCM). The BCM then applies voltage through the backup lamps control circuit to the tail lamp assemblies illuminating the backup lamps.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, place the PRNDL in the REVERSE position. The backup lamps should illuminate.

1. Ignition OFF, disconnect the harness connector at the appropriate tail lamp assembly.
2. Test for less than 5.0 ohm between the ground circuit listed below and ground.

•	RPO WDA - Terminal 2

•	RPO Z88 - Terminal 1

•	RPO W49 - Terminal B

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit listed below and the ground circuit.

•	RPO WDA - Terminal 1

•	RPO Z88 - Terminal 2

•	RPO W49 - 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 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 backup lamp bulb.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.