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
* Body Control System Schematics [1][2]Body Control Systems
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1
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
1. Vehicle in Service Mode, observe the scan tool Brake Pedal Applied parameter while pressing and releasing the brake pedal. The parameter should change between Active and Inactive as the brake pedal is applied and released.
• If the parameter does not change between the commanded states, refer to the Brake Pedal Position Sensor Malfunction.
2. Command the Left Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The left brake lamp should turn ON and OFF when changing between the commanded states.
• If the left brake lamp does not turn ON and OFF when changing between the commanded states, refer to Stop Lamps Malfunction.
3. Command the Right Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The right brake lamp should turn ON and OFF when changing between the commanded states.
• If the right brake lamp does not turn ON and OFF when changing between the commanded states, refer to Stop Lamps Malfunction.
4. Command the Center Brake Lamp ON and OFF with a scan tool. The center high mounted stop lamp should turn ON and OFF when changing between the commanded states.
• If the center high mount stop lamp does not turn ON and OFF when changing between the commanded states, refer to Center High Mount Stop Lamp Malfunction.
Circuit/System Testing
Brake Pedal Position Sensor Malfunction
1. Vehicle OFF, disconnect the harness connector at the B22 brake pedal position sensor.
2. Vehicle in Service Mode, verify that a test lamp does not illuminate between the low reference circuit terminal C and ground.
• If the test lamp illuminates, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
3. If all circuits test normal, replace the B22 brake pedal position sensor.
Stop Lamps Malfunction
1. Vehicle OFF, disconnect the harness connector at the inoperative E42 tail lamp assembly.
2. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 4 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Vehicle in Service Mode, command the appropriate Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, replace the inoperative E42 tail lamp assembly.
Center High Mount Stop Lamp Malfunction
1. Vehicle OFF, disconnect the harness connector at the E6 center high mounted stop lamp.
2. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Vehicle in Service Mode, command the Center Brake Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, replace the E6 center high mounted stop lamp.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Tail Lamp Replacement Tail Lamp Replacement
* High Mount Stop Lamp Replacement Service and Repair
* Control Module References Programming and Relearning for BCM replacement, programming and setup