For 1990-2009 cars

### 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 Lamp Switch B+ | 1 | 1 | -- | --
Backup Lamp Control | 1 | 1 | 1 |
Backup Lamp Ground | -- | 1 | -- | --
1. Backup Lamp Malfunction

### Circuit/System Description

Battery voltage is applied from the BCK/UP LAMP fuse located in the underhood fuse block to the backup lamp switch when the ignition switch is in the RUN or CRANK positions. When the transmission is placed in the REVERSE position, the backup lamp switch closes providing battery voltage to the backup lamp. The backup lamp is permanently grounded at ground G402. With both power and ground, the backup lamp illuminate. Once the driver moves the gear selector out of the REVERSE position, the backup lamp switch contacts open and the backup lamp turns OFF.

### 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 harness connector at the backup lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 2 and ground.

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

3. Connect the harness connector at the backup lamp.
4. Ignition OFF, disconnect the backup lamp switch.
5. Ignition ON, verify that a test lamp illuminates between the control circuit terminal A and ground.

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.

6. Verify that a test lamp does not illuminate between the control circuit terminal B and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

7. Connect a 10-amp fused jumper between the control circuit terminal A and the control circuit terminal B. Verify the backup lamp illuminate.

⇒ | If the backup lamp does not illuminate, test the control circuit terminal B for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the backup lamp.

8. If all circuits test normal, test or replace the backup lamp switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Backup Lamp Replacement

• | Backup Lamp Switch Replacement