Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Brake Position Sensor Signal | C0277 06 | C0277 06 | C0277 07 | C0277 09 |
Brake Position Sensor 5-Volt Reference | C0870 03 | C0870 03 | C0870 07 | -- |
Brake Position Sensor Low Reference | -- | C0277 06 | C0277 07 | -- |
Stop Lamp Switch Signal | B3903 02, P0572 | B3903 05, P0573 | B3903 05, P0573 | -- |
Left Rear Stop/Turn Lamp Supply Voltage | 3 | 3 | 2 | -- |
Right Rear Stop/Turn Lamp Supply Voltage | 3 | 3 | 2 | -- |
Center High Mounted Stop Lamp (CHMSL) Ground | -- | 1 | 1 | -- |
Left Rear Stop/Turn Lamp Ground | -- | 3 | 3 | -- |
Right Rear Stop/Turn Lamp Ground | -- | 3 | 3 | -- |
1. High Mounted Stop Lamp Inoperative 2. Stop Lamps Always On 3. Stop Lamps Inoperative | ||||
Circuit/System Description
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position 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 brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.
Diagnostic Aids
Important: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .
Reference Information
Schematic Reference
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the BCM C3 harness connector.
- Ignition ON, the stop lamps should turn OFF.
- If all circuits test normal, replace the BCM.
| ⇒ | If the stop lamps remain illuminated, repair the stop lamp voltage supply circuits for a short to voltage. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM replacement, setup, and programming
