Backup Lamps Malfunction (Automatic Transmission)
Backup Lamps Malfunction (Automatic 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
Battery voltage is applied to the park/neutral position (PNP) switch when the ignition switch is in the RUN or CRANK positions. When the transmission is placed in the REVERSE position, the PNP switch provides battery voltage to the backup lamps. The backup lamps are permanently grounded. With both power and ground the backup lamps illuminate. Once the driver moves the gear selector out of the REVERSE position, the PNP switch contacts open and the backup lamps turn OFF.
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 (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
Ignition ON, engine running, turn the backup lamps ON and OFF by going between the park and reverse gears. The backup lamps should turn ON and OFF when changing between the selected states.
Circuit/System Testing
1. Ignition OFF, disconnect the backup lamp relay.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the ground circuit terminal 86 and ground.
• 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 B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Connect a test lamp between the control circuit terminal 85 and the ground circuit terminal 86.
5. Turn the backup lamps ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the BCM.
6. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
7. Ignition OFF, disconnect the harness connector at the appropriate backup lamp.
8. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the backup lamp ground circuit terminal G and ground
• If greater than the specified range, test the ground circuit for an open/high resistance.
9. Connect the harness connector at the backup lamp.
10. Ignition ON, connect a 15 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the backup lamp is activated.
• If the backup lamp does not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the backup lamp.
11. If all circuits test normal, test or replace the backup lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Tail Lamp Replacement (Service and Repair)
* Backup Lamp Bulb Replacement (Service and Repair)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness)) Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming