Stop Lamps Malfunction

Stop Lamps Malfunction

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.



Circuit/System Description

The body control module (BCM) is responsible for controlling the stop lamps. When the driver presses the brake pedal, the BCM will receive a signal from the brake pedal position sensor. The BCM then supplies battery positive voltage to both left and right stop lamp assemblies and to the center high mounted stop lamp (CHMSL). The stop lamps are grounded at G401 and G403. The CHMSL is grounded at G302.


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) for scan tool information


Circuit/System Verification

1. Brake pedal unapplied, observe the stop lamps. The stop lamps should not be illuminated.

• If the stop lamps are illuminated, refer to Stop Lamps Always On.

2. Refer to Stop Lamps Inoperative.



Circuit/System Testing


Stop Lamps Always On
1. Verify the scan tool BPPS Voltage parameter is less than 1 volt.

• If not the specified value, recalibrate the BPPS. If the scan tool BPPS Voltage parameter is not less than 1 volt, replace the BPPS.

2. If all circuits test normal, replace the BCM.



Stop Lamps Inoperative
1. Ignition OFF, disconnect the harness connector at the inoperative stop lamp.
2. Verify that a test lamp illuminates between the ground circuit terminal G and B+.

• If the test lamp does not illuminate, test the ground circuit terminal G for a short to voltage or an open/high resistance.

3. Test the voltage supply circuit terminal A for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Brake Pedal Position Sensor Replacement (Brake Pedal Position Sensor Replacement)
* Brake Pedal Position Sensor Calibration (Programming and Relearning)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming