5. If all circuits test normal, test or replace the headlamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Headlamp Switch Replacement (Cadillac) (See: Lighting and Horns/Headlamp/Headlamp Switch/Service and Repair/Headlamp Switch
Replacement (Cadillac)) Headlamp Switch Replacement (Except Cadillac) (See: Lighting and Horns/Headlamp/Headlamp Switch/Service
and Repair/Headlamp Switch Replacement (Except Cadillac))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for XBCM replacement, setup, and programming
B2545
DTC B2545
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC B2545 00
- Backup Lamps Circuit
Diagnostic Fault Information
Circuit/System Description
When the transmission is placed 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 voltage to the backup lamp relay
control circuit energizing the backup lamp relay coil. With the relay coil energized, the switch contacts close allowing battery voltage to flow
through the VEH BCK/UP fuse to the left and right backup lamps. The BCM also supplies voltage the to inside rearview mirror via the backup lamp
relay control circuit for automatic day/night operation. Once the driver moves the gear selector out of the REVERSE position, a serial data message
is sent by the TCM requesting the BCM to remove voltage from the backup lamp control circuit.
Conditions for Running the DTC
Battery voltage must be between 9-16 V.
Conditions for Setting the DTC
The BCM detects a short to ground in the backup lamp relay control circuit.
Action Taken When the DTC Sets
The backup lamps will not operate.
Conditions for Clearing the DTC
* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.
