C1281

DTC C1281

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC C1281
- Master Cylinder Pressure Sensor Signal

Circuit/System Description

The master cylinder pressure sensor is part of the electronic brake control module (EBCM).

Conditions for Running the DTC

The vehicle speed is at least 7 km/h (4 mph).

Conditions for Setting the DTC

The EBCM detects an incorrect master cylinder pressure sensor voltage.

Action Taken When the DTC Sets

* The ABS warning indicator turns ON.
* The ABS is disabled.
* The vehicle stability control (VSC) warning indicator turns ON.
* The VSC is disabled.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Reference Information
Schematic Reference

Antilock Brake System Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

ABS Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Verify the brake lamps operate?

• If brake lamps do not operate, refer to appropriate diagnosis.

2. Using a scan tool, monitor the master cylinder pressure is 0.3-0.9V with brake pedal released and increases to a maximum of 5V with pedal depressed.

• If master cylinder pressure is not as specified, replace the BPMV.

Circuit/System Testing

1. Using a scan tool, monitor that the brake lamp switch status changes as the brake pedal is applied and released.

• If brake lamp switch status changes as specified, replace the BPMV.

2. Ignition OFF, disconnect the EBCM connector.
3. Ignition ON, check for 8-14V between EBCM connector terminal 2 and ground with brake pedal applied and less than 1.5V with braked pedal released.

• If the voltage is not as specified, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BPMV/EBCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Brake Pressure Modulator Valve Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for EBCM replacement, setup, and programming