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 engine control module (ECM) provides a signal circuit to the backup lamp switch which is permanently grounded. When the transmission is placed in the REVERSE position, the backup lamp switch signal circuit is pulled low and the ECM responds by sending a serial data message to the body control module (BCM). The message indicates that the gear selector is in the REVERSE position. The BCM applies battery voltage to the backup lamps which are permanently grounded. Once the driver moves the gear selector out of the REVERSE position, a message is sent by the ECM via serial data requesting the BCM to remove battery voltage from the backup lamps control circuit.
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)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, engine running, command the Backup Lamps Relay Command 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 turn ON and OFF when changing between the commanded states, refer to Backup Lamps Switch Malfunction.
2. Engine running, shift the vehicle between the park and reverse gears. The backup lamps should turn ON and OFF when changing between the selected states.
• If the backup lamps do not turn ON and OFF when changing between the selected states, refer to Backup Lamps Malfunction.
Circuit/System Testing
Backup Lamps Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the B16 backup lamp switch.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohm between the ground circuit terminal listed below and ground.
* Terminal B (M10)
* Terminal 2 (MV5)
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the signal circuit terminal listed below and ground.
* Terminal A (M10)
* Terminal 1 (MV5)
• If the test lamp does not illuminate, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
4. Install a 3 A fused jumper wire between the signal circuit terminal and the ground circuit terminal. The backup lamps should illuminate.
• If the backup lamps do not illuminate, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
5. If all circuits test normal, test or replace the B16 backup lamp switch.
Backup Lamps Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate E5 backup lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohm 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 a test lamp between the control circuit terminal 1 and ground.
4. Engine running, command the Backup Lamps 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 K9 BCM.
• 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 K9 BCM.
5. If all circuits test normal, test or replace the E5 backup lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Backup Lamp Replacement (Service and Repair)
* Backup Lamp Switch Replacement (Tremec 6-Speed - Manual Transmission)
* Control Module References (Programming and Relearning) for ECM or BCM replacement, setup, and programming