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 stop lamp control circuit illuminating the left and right tail/stop and turn signal lamps and the center high mounted stop lamp. The BCM also applies battery voltage to the transmission control module (TCM) and engine control module (ECM) via the brake applied signal circuit.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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 Applied Output Signal 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 brake lamps turns ON and OFF when commanding the Brake Lamp Command ON and OFF with a scan tool.
• If the brake lamps do not turn ON and OFF
Refer to Stop Lamps Malfunction.
• If the brake lamps turn ON and OFF
4. Verify the center high mounted stop lamp turns ON and OFF when commanding the Center Brake Lamp Command 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
5. 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 2 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, trunk latch latched, disconnect the harness connector at the appropriate tail/stop lamp.
2. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.
* E42L tail lamp assembly - left terminal 1
* E42R tail lamp assembly - right terminal 1
* E5W tail/stop and turn signal lamp - left outer terminal 1
* E5AE tail/stop and turn signal lamp - left inner terminal 1
* E5X tail/stop and turn signal lamp - right outer terminal 1
* E5AF tail/stop and turn signal lamp - right inner terminal 1
• 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 appropriate control circuit terminal listed below and ground, ignition ON.
* E42L tail lamp assembly - left terminal 2
* E42R tail lamp assembly - right terminal 2
* E5W tail/stop and turn signal lamp - left outer terminal 3
* E5AE tail/stop and turn signal lamp - left inner terminal 3
* E5X tail/stop and turn signal lamp - right outer terminal 3
* E5AF tail/stop and turn signal lamp - right inner terminal 3
4. Verify the test lamp turns ON and OFF when commanding the Brake Lamp Command 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
* X5
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
* X5
1. 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 tail/stop lamp.
Center High Mount Stop Lamp Malfunction
1. Ignition OFF, exterior lamps OFF, trunk latch latched, disconnect the harness connector at the E6 center high mounted stop lamp.
2. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.
* Terminal 2 - coupe
* Terminal B - convertible
• 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 appropriate control circuit terminal listed below and ground, ignition ON.
* Terminal 1 - coupe
* Terminal A - convertible
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 (Coupe) High Mount Stop Lamp Replacement (Coupe)High Mount Stop Lamp Replacement (ZL1) High Mount Stop Lamp Replacement (ZL1)High Mount Stop Lamp Replacement (Convertible) High Mount Stop Lamp Replacement (Convertible)
* Tail Lamp Bulb Replacement Service and Repair
* Brake Pedal Position Sensor Replacement Service and Repair
* Tail Lamp Replacement - Inboard Tail Lamp Replacement - Inboard
* Tail Lamp Replacement - Outboard Tail Lamp Replacement - Outboard
* Control Module References Control Module References for BCM replacement, programming, and setup