Stop Lamps Malfunction

Stop Lamps Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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.

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 after completing the diagnostic procedure. Verification Tests

* Brake Pedal Position Sensor Replacement
* Brake Pedal Position Sensor Calibration