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 positive 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 power through the stop lamps fuse to illuminate the stop lamps.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0277 Brake Pedal Position Sensor Circuit

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

DTC Symptom | DTC Symptom Descriptor
--- | ---
03 | Voltage Below Threshold
07 | Voltage Above Threshold
09 | Rate of Change Above Threshold

### Conditions for Running the DTC

Ignition voltage is within the normal operating voltage range.

### Conditions for Setting the DTC

#### C0277 03

The IPM detects an open or short to ground in the BPP sensor circuit for 0.5 second or greater.

#### C0277 07

The IPM detects a short to battery voltage in the BPP sensor or low reference circuits for 0.5 second or greater.

#### C0277 09

The IPM detects the BPP signal is changing faster than possible under normal operating conditions.

### Action Taken When the DTC Sets

• | The Service Vehicle Soon indicator is commanded ON.

• | When DTC C0277 is set as current, the vehicle will not start.

• | If the DTC sets while the vehicle is running, the IPM will activate the brake lights when the vehicles transmission is not in the PARK position and the vehicle is not accelerating.

### Conditions for Clearing the DTC

• | 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.

• | A DTC will not clear the current status until the next ignition cycle.

### 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 C0277 09 is set, replace the BPP sensor. If the DTC resets, replace the IPM.

• | 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.
3. With a scan tool, observe the Brake Pedal Position (BPP) Sensor parameter in the instrument panel module (IPM) data list.
4. Apply and release the brake pedal.

Does the scan tool display a change in BPP Sensor Counts?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3 | Is DTC C0277 09 present? | Go to Step 9 | Go to Step 4
4 | Is DTC C0277 07 present? | Go to Step 5 | Go to Step 8
5 |

1. Turn OFF the ignition.
2. Disconnect the IPM C3 harness connector.
3. Connect a test lamp between the BPP sensor signal circuit and ground.

Does the test light illuminate?

Go to Step 6

Go to Step 12

6 | Test the BPP sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 7
7 | Test the BPP sensor low reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 9
8 | Test the BPP sensor signal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 9
9 | Inspect for poor connections at the BPP sensor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 10
10 | 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 repair? | Go to Step 11 | --
11 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Apply and release the brake pedal.

Does the scan tool display DTC C0277 as current?

Go to Step 12

Go to Step 14

12 | Inspect for poor connections at the IPM C3 harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 14 | Go to Step 13
13 | Replace the IPM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 14 | --
14 |

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