Backup Lamps Malfunction (Manual Transmission)
Backup Lamps Malfunction (Manual Transmission)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The underhood electrical center (UEC) provides the normally open backup lamp switch with voltage. When the transmission is placed in the reverse position, the backup lamp switch closes providing a ground path through G104. The UEC responds to the flow of voltage by sending a serial data message to the rear electrical center (REC) requesting the backup lamps be illuminated. The REC applies battery voltage to the backup lamps control circuit illuminating the backup lamps. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the UEC via serial data requesting the REC to remove battery voltage from the backup lamps control circuit. The backup lamps are permanently grounded at G403.
Reference Information
Schematic Reference
Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
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 Verification
1. Ignition ON, observe the scan tool Reverse Gear Switch parameter while operating the gear selector in and out of the reverse position. The parameter should change between Active and Inactive as the gear selector is operated.
• If the parameter does not change as the gear selector is operated, refer to Backup Lamp Switch Malfunction.
2. With a scan tool, command the Reverse Light Test ON and OFF. The backup lamps should turn ON and OFF when commanded.
• If the backup lamps do not illuminate when commanded, refer to Backup Lamps Malfunction.
Circuit/System Testing
Backup Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the backup lamp switch.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal A and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Reverse Gear Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the UEC.
4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool Reverse Gear Switch parameter is Active.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the UEC.
5. If all circuits test normal, replace the backup lamp switch.
Backup Lamps Malfunction
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 appropriate ground circuit terminal listed below and ground.
* Left tail lamp ground terminal 1 - 3 Door
* Left tail lamp ground terminal 6 - 5 Door
* Right tail lamp ground terminal 6 - 3 Door
* Right tail lamp ground terminal 1 - 5 Door
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the appropriate control circuit terminal listed below and ground.
* Left backup lamp control terminal 2 - 3 Door
* Left backup lamp control terminal 1 - 5 Door
* Right backup lamp control terminal 5 - 3 Door
* Right backup lamp control terminal 6 - 5 Door
4. Command the Reverse Light Test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the REC.
• 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 REC.
5. If all circuits test normal, replace the inoperative tail lamp circuit board.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Tail Lamp Circuit Board Replacement (Service and Repair)
* Backup Lamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for REC or UEC replacement, setup, and programming