Backup Lamps Malfunction

Backup Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

The BCK/UP fuse in the underhood fuse block supplies B+ to the normally open park/neutral position (PNP) switch used in a vehicle equipped with an automatic transmission or the backup lamp switch if equipped with a manual transmission. When the driver places the gear select lever in the REVERSE position, the switch closes and the current flows through the switch to the backup lamps. The backup lamps are grounded at G350 and G340.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Testing

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 park/neutral position switch - with M30 or the backup lamp switch - with MA5.
5. Ignition ON, verify that a test lamp illuminates between the appropriate control circuit terminal listed below and ground.

* Park/neutral position switch terminal 11 - with M30
* Backup lamp switch terminal A - with MA5

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

6. Connect a 15 amp fused jumper wire between the appropriate control circuit terminals listed below. Verify the backup lamps illuminate.

* Park/neutral position switch terminal 11 and terminal 10 - with M30
* Backup lamp switch terminal A and terminal B - with MA5

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

* Park/neutral position switch terminal 10 - with M30
* Backup lamp switch terminal B - with MA5

7. If all circuits test normal, test or replace the park/neutral position switch or the backup lamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Backup Lamp Switch Replacement (Service and Repair)
* Backup Lamp Bulb Replacement (Service and Repair)