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

Backup Lamp Relay B+

1

1

--

--

Backup Lamp Relay Control

1

1

B2545 00

--

Backup Lamps Control

1

1

1

--

Backup Lamp Ground - Left

--

1

--

--

Backup Lamp Ground - Right

--

1

--

--

1. Backup Lamps Malfunction

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 ground 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 from the BACKUP LP fuse to the left and right backup lamps. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the TCM via serial data requesting the BCM to remove ground from the backup lamp relay control circuit.

Conditions for Running the DTC

    • Battery voltage must be between 9-16 volts.
    • Backup lamps commanded ON.

Conditions for Setting the DTC

DTC B2545 00 will set when the BCM detects a short to voltage in the backup lamp relay control circuit.

Actions Taken When the DTC Sets

When DTC B2545 00 is present, 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.

Reference Information

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

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Ignition OFF, disconnect the backup lamp relay.
  2. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
  3. Command the Backup Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  4. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
    If the test lamp is always OFF, test the control circuit for a short to voltage 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 relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for BCM replacement, setup, and programming