Circuit Description
The brake pedal position (BPP) sensor provides an analog pedal position signal. Its output is hardwired to the electro-hydraulic power steering (EHPS) module connector. The signal must be digitized and differentiated within the EHPS module to provide the necessary pedal rate signal.
The BPP sensor is a resistive sensor with a total resistance between 3 k - 5 k ohms with a maximum current draw of less than 16 ma. The BPP sensor will output an analog signal that is referenced to 5 volts which may increase or decrease monotonically with brake pedal depression. The sensor analog output shall have a specified electrical output over a mechanical range of 32 degrees rotation of the brake pedal pivot. Out-of-range values will be provided outside of the 32 degrees range.
The EHPS provides a GMLAN message to the vehicle which indicates the translation of the brake pedal. Due to build variance, the EHPS can not be certain what BPP sensor signal voltage represents a brake pedal position at rest. The EHPS needs the zero reference to provide brake pedal position. The EHPS receives a control packet identifier (CPID) request from a scan tool to calibrate the zero reference position (learn home).
DTC C0278 can be set for the two following reasons:
| • | A new EHPS has been installed. A traceability request or the ignition is cycled 255 times before receiving a learn home request. |
| • | The EHPS receives the learn home request and the BPP sensor is not within a valid range. If there is a hardware problem or the operators foot is on the pedal, the zero reference read will not execute. |
Calibration of the BPP sensor is performed whenever the BPP sensor is replaced or the EHPS system has been serviced.
Conditions for Running the DTC
| • | EHPS module in RUN mode. |
| • | Ignition switch in ACC or ON position |
| • | Battery voltage between 12-58 volts. |
Conditions for Setting the DTC
EHPS has never received a learn home command or when the learn home calibration is received, the difference between the brake pedal position nominal position and the actual position is greater than 44.92 mm (1.76 in) or is less than -44.92 mm (-1.76 in).
Action Taken When the DTC Sets
| • | System operation is reduced. |
| • | The SERVICE BRAKE SYSTEM message will be displayed. |
| • | Ramp the motor speed input to the commanded flow resolved from a default brake pedal position. |
| • | Stores DTC C0282 in the powertrain control module (PCM). |
| • | History DTC C0282 will be set in PCM. |
Conditions for Clearing the DTC
| • | A successful learn home calibration has been performed. |
| • | Using the scan tool. |
| • | A history DTC will clear after 255 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
It may be necessary to check Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step calibrates the BPP sensor.
-
This step checks to see if the DTC C0278 resets.
-
This step checks for poor connections at the BPP sensor harness connector.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Power Steering Schematics Connector End Views Reference: Power Steering Connector End Views | ||||
1 | Did you perform the electro-hydraulic power steering (EHPS) Diagnostic System Check? | -- | Go to Step 2 | |
|
Important: Ensure that the fork of the brake pedal position (BPP) sensor is properly aligned on the pin attached to the brake pedal.
Important: The CANdi module must be attached to the scan tool. Did you complete the calibration procedure? | -- | Go to Step 3 | -- | |
Does the DTC reset? | -- | Go to Step 4 | Go to Step 6 | |
Inspect for poor connections at the harness connector of the BPP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 5 | |
5 |
Important: Always perform the calibration procedure for the BPP sensor. Refer to Brake Pedal Position Sensor Calibration Description and Operation . Replace the BPP 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 |
