Stop Lamps Malfunction

Stop Lamps Malfunction

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 brake pedal position (BPP) sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position (BPP) sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5 V reference voltage to the brake pedal position (BPP) sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the stop lamp control circuit and center high mounted stop lamp control circuit. When the control circuit is energized the stop lamps are illuminated.

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, observe the scan tool Brake Switch parameter. The reading should be between Inactive/Active and change when the brake pedal is pushed or released.
* Ignition ON, perform the Brake Lamp test. The brake lamps should be ON/OFF.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B22 Brake Pedal Position Sensor.
2. Ignition OFF, test for less than 5 ohm between the low reference circuit terminal 3 and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

3. Ignition ON, command the Brake Lamp Command test with a scan tool. The brake lamps should turn ON and OFF when changing between the commanded states.

• If the brake lamps did not turn ON and OFF replace the K9 Body Control Module.

Repair Instructions

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

* Tail Lamp Replacement (Service and Repair)
* High Mount Stop Lamp Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming