For 1990-2009 cars

### Circuit Description

The brake pedal position (BPP) sensor is used to sense the action of the driver's application of the brake pedal. The BPP sensor provides an analog voltage signal that will increase as the brake pedal is applied. The instrument panel module (IPM) 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 IPM will apply battery voltage to the center high mounted stop lamp (CHMSL), transmission control module (TCM), engine control module (ECM), and stop lamp relay coil. When the stop lamp relay receives battery voltage from the IPM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the stop lamps fuse to illuminate the stop lamps.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0278 Brake Pedal Position Sensor Not Calibrated

The vehicle has DTCs including the DTC symptoms. Refer to DTC Symptom Description for more DTC symptoms.

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 BPP 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 BBP 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 BPP 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 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.

Does the scan tool display DTC C0278 00 as current?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3 | Attempt to recalibrate the brake pedal position (BPP) sensor. Refer to Brake Pedal Position Sensor Calibration . Did you complete the repair? | Go to Step 4 | --
4 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.

Does the scan tool indicate DTC C0278 00 as current?

Go to Step 5

Go to Step 6

5 | Important: Recalibrate the BPP sensor after replacement. Refer to Brake Pedal Position Sensor Calibration . Replace the BPP sensor. Refer to Brake Pedal Position Sensor Replacement . Did you complete the replacement? | Go to Step 6 | --
6 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK