Backup Lamps Malfunction (Manual Transmission)
Backup Lamps Malfunction (Manual Transmission)
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. With the engine ON and the transmission 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 control circuit illuminating the backup lamps. 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. The engine must be ON for the backup lamps to operate.
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
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. Engine ON, observe the scan tool Reverse Position Switch parameter in the ECM data list while shifting the vehicle between the neutral and reverse gears. The reading should change between ON and OFF when changing between the selected states.
• If the reading does not change between the specified values, refer to Backup Lamp Switch Malfunction.
2. 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 turn ON and OFF when changing between the commanded states, refer to Backup Lamps Malfunction.
Circuit/System Testing
Backup Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the B16 backup lamp switch.
2. Ignition OFF, exterior lamps OFF, doors CLOSED, wait 30 seconds, test for less than 5 ohms between the ground circuit terminal 2 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 Position Switch parameter is OFF.
• If not the specified value, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the K20 engine control module.
4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the ground circuit terminal 2. Verify the scan tool Reverse Position Switch parameter is ON.
• 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 K20 engine control module.
5. If all circuits test normal, 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 ohms between the ground circuit terminal 3 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 2 and ground.
4. Ignition ON, 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 control circuit for a short to voltage. If the circuit tests normal, replace the K9 body control module.
• 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 body control module.
5. If all circuits test normal, replace the E5 backup lamp.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Tail Lamp Bulb Replacement Service and Repair
* Backup Lamp Switch Replacement Service and Repair
* Control Module References Programming and Relearning for BCM or ECM replacement, setup, and programming