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 fuse block supplies battery voltage through the STOP/B/U/ LPS fuse to the coil and switch terminals of the BCK/UP LAMP Relay located in the body control module (BCM). The BCM provides the normally open reverse switch with voltage. When the transmission is placed in the reverse position, the reverse switch closes providing a ground path through the reverse lamp relay control circuit to the BCM. The BCM then grounds the back up lamp relay control circuit of the backup lamp relay . This energizes the backup lamp relay, closing the switch side contacts and provides battery voltage to the REVERSE LAMPS fuse through to the backup lamps. The backup lamps are permanently grounded at G302. Once the driver moves the gear selector out of the REVERSE position, the reverse switch opens and the BCM removes ground from the backup lamp relay control circuit. This opens the backup lamp relay switch contacts turning OFF the backup lamps.
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)
Circuit/System Testing
1. Ignition OFF, disconnect the backup lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit and ground.
• If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.
3. Verify that a test lamp illuminates between the relay coil B+ circuit and ground.
• If the test lamp does not illuminate, test the relay coil B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the backup lamp relay.
4. Verify that a test lamp illuminates between the relay switch B+ circuit and ground.
• If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the inoperative backup lamp.
6. Test for less than 5.0 ohms of resistance between the inoperative backup lamp ground circuit terminal 1 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the inoperative backup lamp.
8. Connect a 10A fused jumper wire between the relay switch B+ circuit and the relay controlled output circuit. Verify the backup lamps are activated.
• If the backup lamps do not activate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative backup lamp.
9. Connect a test lamp between the relay coil B+ circuit and the relay coil control circuit.
10. Command the backup lamps 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 relay coil control circuit for a short to ground. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
11. Connect the backup lamp relay.
12. Command the backup lamps ON and OFF with a scan tool. The backup lamps should turn ON and OFF when changing between the commanded states.
• If the backup lamps do not activate, replace the backup lamp relay.
13. Ignition OFF, disconnect the harness connector at the reverse lamp switch.
14. Test for less than 5.0 ohms of resistance between the control circuit terminal 1 and ground.
• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If circuits test normal, replace the BCM.
15. Ignition OFF, disconnect the X2 harness connector at the BCM.
16. Verify a test lamp does not illuminate between B+ and the relay control circuit terminal 1 at the reverse lamp switch harness connector.
• If the test lamp illuminates, test the relay control circuit for a short to ground.
17. Reconnect the X2 harness connector at the BCM.
18. Ignition ON, verify a test lamp illuminates between the supply voltage circuit terminal 2 and ground.
• If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
19. If all circuits test normal, test or replace the reverse lamp switch.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Backup Lamp Replacement (Service and Repair)
* Backup Lamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming