GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • 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.

DTC Descriptor

DTC B2545 00: Backup Lamps Circuit

Diagnostic Fault Information

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

--

  1. Backup lamps inoperative
  2. Backup lamps always on

Circuit/System Description

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.

Conditions for Running the DTC

    • The ignition is ON
    • The backup lamps must be commanded ON.

Conditions for Setting the DTC

The BCM detects a short to ground on the backup lamp supply voltage circuit.

Action Taken When the DTC Sets

The BCM will deactivate the backup lamps for the remainder of the ignition cycle.

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.

Reference Information

Schematic Reference

Fog Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

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

Circuit/System Testing

  1. Ignition OFF, disconnect the C4 harness connector at the BCM.
  2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 4 and ground.
  3. 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.

    BCM C6 Harness Connector Terminal 2

    • Left backup lamp
    • Right backup lamp
  4. If all circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Backup Lamp Bulb Replacement
    •  Inside Rearview Mirror Replacement
    •  Control Module References for BCM replacement, setup, and programming