Circuit 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, transmission control module (TCM), engine control module (ECM), and stop lamp relay coil side. The BCM also supplies the stop lamp relay coil with ground. When the stop lamp relay receives battery voltage and ground from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the STOP/B/U/LPS fuse to illuminate the center high mounted stop lamp (CHMSL).
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0278 Brake Pedal Position Sensor Not Calibrated
DTC Symptom | DTC Symptom Descriptor |
|---|---|
00 | No Additional Information |
Conditions for Running the DTC
Ignition voltage is within the normal operating voltage range.
Conditions for Setting the DTC
DTC C0278 00 will set when the brake pedal position sensor home position is not learned.
Action Taken When the DTC Sets
| • | The Service Vehicle Soon indicator is commanded ON. |
| • | When DTC C0278 is set as current, the vehicle will not start. |
| • | Stop lamps may not activate at the expected brake pedal positions. |
Conditions for Clearing the DTC
| • | A successful brake pedal position sensor calibration has been performed. |
| • | The condition responsible for setting the DTC no longer exists. |
| • | You issue a scan tool CLEAR DTCs command. |
| • | A history DTC will clear once 50 malfunction-free ignition cycles have occurred. |
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 .
| • | If DTC C0278 00 is set, recalibrate the brake pedal position sensor. |
| • | Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections . |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the scan tool display DTC C0278 00? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections |
3 | Attempt to recalibrate the brake pedal position sensor. Refer to Brake Pedal Position Sensor Calibration . Did you complete the repair? | Go to Step 4 | -- |
4 |
Does the scan tool display DTC C0278 00 as current? | Go to Step 5 | Go to Step 6 |
5 |
Important: Recalibrate the brake pedal position sensor after replacing. Refer to Brake Pedal Position Sensor Calibration . Replace the brake pedal position sensor. Refer to Brake Pedal Position Sensor Replacement . Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
