For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Backup Lamps Voltage Supply | B2530 | 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 back up 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 1.0 ohm of resistance between the ground circuit terminal B and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the voltage supply circuit terminal A and the ground circuit terminal B.
4. Ignition ON, place the PRNDL in the reverse position. The test lamp should turn ON and OFF when changing between park and reverse.

⇒ | If the test lamp is always ON, test the control 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 control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the body control module.

5. If all circuits test normal, test or replace the appropriate component.

### Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Tail Lamp Bulb Replacement

• | Tail Lamp Replacement

• | Inside Rearview Mirror Replacement

• | Control Module References for BCM replacement, setup, and programming