| • | 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. | 
Circuit  | Short to Ground  | Open/High Resistance  | Short to Voltage  | Signal Performance  | 
|---|---|---|---|---|
B+, BCM C4 terminal 4  | B2545 00  | B2545 00  | --  | --  | 
Backup Lamps Voltage Supply  | B2545 00  | 1  | 2  | --  | 
  | ||||
When the PRNDL is placed in the REVERSE position, a GMLAN serial data message is sent from the transmission control module to the body control module (BCM). In response to this message, the BCM applies battery voltage from the CHMSL/BCK-UP fuse through the backup lamps supply voltage circuit illuminating the left and right backup lamps.
| • | The ignition is ON | 
| • | The backup lamps must be commanded ON. | 
The BCM detects a short to ground on the backup lamp supply voltage circuit.
The BCM will deactivate the backup lamps for the remainder of the ignition cycle.
| • | The condition responsible for setting the DTC no longer exists. | 
| • | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. | 
Lighting Systems Connector End Views
Ignition ON, place the PRNDL to the REVERSE position. The backup lamps should illuminate.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the supply voltage circuit and components listed below for a short to ground. | 
| • | Left backup lamp | 
| • | Right backup lamp | 
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |