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.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Backup Lamps Voltage Supply

B2545 00

1

1

--

1. Backup Lamps Inoperative

Circuit/System Description

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

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

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 in the REVERSE position. The backup lamps should illuminate.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate tail lamp assembly.
  2. Test for less than 5.0 ohms of resistance between the ground circuit terminal 3 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Connect a test lamp between the supply voltage circuit terminal 1 and the ground circuit terminal 3.
  5. 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.
  6. If the test lamp is always ON, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the body control module.
    If the test lamp is always OFF, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the body control module.
  7. If all circuits test normal, test or replace the appropriate component.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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