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 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-volt reference voltage to the BPP sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery voltage to the left and right stop lamp control circuits as well as the center high mounted stop lamp (CHMSL) control circuit illuminating the left and right stop lamps and the CHMSL.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views Outside Rearview Mirror - Driver
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 Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify the scan tool Brake Pedal Applied parameter changes between Active and Inactive while pressing and releasing the brake pedal.
• If the parameter does not change
Refer to Brake Pedal Position Sensor Malfunction.
• If the parameter changes
3. Verify the left brake lamp turns ON and OFF when commanding the Left Brake Lamp ON and OFF with a scan tool.
• If the left brake lamp does not turn ON and OFF
Refer to Stop Lamps Malfunction.
• If the left brake lamp turns ON and OFF
4. Verify the right brake lamp turns ON and OFF when commanding the Right Brake Lamp ON and OFF with a scan tool.
• If the right brake lamp does not turn ON and OFF
Refer to Stop Lamps Malfunction.
• If the right brake lamp turns ON and OFF
5. Verify the center high mounted stop lamp turns ON and OFF when commanding the Center Brake Lamp ON and OFF with a scan tool.
• If the center high mounted stop does not turn ON and OFF
Refer to Center High Mount Stop Lamp Malfunction.
• If the center high mounted stop turns ON and OFF
6. All OK.
Circuit/System Testing
Brake Pedal Position Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the B22 brake pedal position sensor, ignition ON.
2. Test for less than 1 V between the low reference circuit terminal 1 and ground.
• If 1 V or greater
1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module.
2. Test for less than 1 V between the low reference circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If less than 1 V
3. Test or replace the B22 brake pedal position sensor.
Stop Lamps Malfunction
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E42 tail lamp assembly.
2. Test for less than 5 ohms between the ground circuit terminal A and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Connect a test lamp between the control circuit terminal B and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the appropriate Brake Lamp ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 body control module.
* X4 left stop lamp
* X5 right stop lamp
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 body control module.
* X4 left stop lamp
* X5 right stop lamp
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the appropriate E5 brake lamp.
Center High Mount Stop Lamp Malfunction
1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the E6 center high mounted stop lamp.
2. Test for less than 5 ohms between the ground circuit terminal 2 and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Connect a test lamp between the control circuit terminal 1 and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the Center Brake Lamp ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X4 harness connector at the K9 body control module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the control circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 body control module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X4 harness connector at the K9 body control module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 body control module.
• If the test lamp turns ON and OFF
5. Test or replace the E6 center high mounted stop lamp.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* High Mount Stop Lamp Replacement High Mount Stop Lamp Replacement
* Tail Lamp Bulb Replacement Service and Repair
* Brake Pedal Position Sensor Replacement
* Brake Pedal Position Sensor Calibration
* Control Module References Control Module References for BCM replacement, programming, and setup