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+ -- Manual Transmission | 1 | 1 | -- | --
Park/Neutral Position Switch B+ -- Automatic Transmission | 1 | 1 | -- | --
Backup Lamp Control | 1 | 1 | 1 | --
Backup Lamp - Left Ground | -- | 1 | -- | --
Backup Lamp - Right Ground | -- | 1 | -- | --
1. Backup Lamps Malfunction

### Circuit/System Description

#### Manual Transmission

Battery voltage is applied 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 provides battery voltage to the backup lamps. The backup lamps are permanently grounded at G105. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, the backup lamp switch contacts open and the backup lamps turn OFF.

#### Automatic Transmission

Battery voltage is applied to the park/neutral position (PNP) switch when the ignition switch is in the RUN or CRANK positions. When the transmission is placed in the REVERSE position, the PNP switch provides battery voltage to the backup lamps. The backup lamps are permanently grounded at G105. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, the PNP switch contacts open and the backup lamps turn 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

#### Backup Lamps Malfunction - Automatic Transmission

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

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

3. Connect the harness connector at the inoperative backup lamp.
4. Ignition OFF, disconnect the harness connector at 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 15-amp fused jumper between the control circuit terminal A and the control circuit terminal B. Verify the backup lamps illuminate.

⇒ | If the backup lamps do 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 inoperative backup lamp.

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

#### Backup Lamps Malfunction - Manual Transmission

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

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

3. Connect the harness connector at the inoperative backup lamp.
4. Ignition OFF, disconnect the harness connector at the PNP switch.
5. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 11 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 10 and ground.

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

7. Connect a 15-amp fused jumper between the control circuit terminal 11 and the control circuit terminal 10. Verify the backup lamps illuminate.

⇒ | If the backup lamps do not illuminate, test the control circuit terminal 10 for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the inoperative backup lamp.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Tail Lamp Replacement

• | Backup Lamp Bulb Replacement

• | Park/Neutral Position and Backup Lamp Switch Replacement