Backup Lamps Malfunction (AT)
Backup Lamps Malfunction (AT)
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
When the automatic transmission is placed in the reverse position, the transmission control module (TCM) sends 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. The backup lamps are permanently grounded. Once the driver moves the gear selector out of the reverse position, a message is sent by the TCM via serial data requesting the BCM to remove battery voltage from the backup lamp control circuit.
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
Ignition ON, perform the Backup Lamps Relay test. The backup lamp should be ON/OFF.
Circuit/System Testing
Observe the parameter Tap Up/Down Switch when putting the gear selector is in the reverse position. The parameter Tap Up/Down Switch should display that reverse gear is engaged.
If the Tap Up/Down Switch parameter displays the corresponding gear, replace the K9 Body Control Module.
If the Tap Up/Down Switch parameter does not displays the corresponding gear, refer to Transmission Control Lever Malfunction (Transmission Control Lever Malfunction).
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Tail Lamp Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming