C12B4

DTC C012A, C128B, C128E, or C12B2-C12B4

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 Descriptors
DTC C012A 00
- Master Cylinder Pressure Sensor

DTC C128E
- Master Cylinder Pressure Sensor

DTC C012A 01
- Master Cylinder Pressure Sensor Short to Battery

DTC C12B3
- Master Cylinder Pressure Sensor Short to Battery

DTC C012A 06
- Master Cylinder Pressure Sensor Short to Ground or Open

DTC C12B2
- Master Cylinder Pressure Sensor Short to Ground or Open

DTC C012A 11
- Master Cylinder Pressure Sensor Above Maximum Threshold

DTC C128B
- Master Cylinder Pressure Sensor Above Maximum Threshold

DTC C012A 0F
- Master Cylinder Pressure Sensor Erratic

DTC C12B4
- Master Cylinder Pressure Sensor Erratic

Circuit/System Description

The electronic brake control module (EBCM) uses input from the master cylinder pressure sensor for more accurate control during a vehicle stability enhancement system event. The master cylinder pressure sensor is internal to the brake pressure modulator valve.

Conditions for Running the DTC

* The ignition is ON.
* Ignition voltage is greater than 10 volts.
* The brake pedal is not applied.

Conditions for Setting the DTC

C012A 00, C128E or C128B

Internal sensor failure is detected.

C012A 11

Improper relearn performed

C012A 01 or C12B3

A short to battery is detected on the sensor signal circuit.

C012A 06 or C12B2

A short to ground or open is detected signal circuit.

C012A OF or C12B4

Signal is erratic and changes faster than physically allowed.

Action Taken When the DTC Sets

* The EBCM disables the ABS and vehicle stability enhancement system for the duration of the ignition cycle.
* A driver information center message and/or a warning indicator may be displayed.

Conditions for Clearing the DTC

* The condition for setting the DTC is no longer present.
* The EBCM clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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 (ABS Hybrid (HP2))
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. Using a scan tool, perform the EBCM, Module Setup, EBCM Relearn.
2. Verify that DTC C012A, C128B, C128E, C12B2, C12B3, or C12B4 is not set.

• If the DTC is set replace brake pressure modulator valve assembly. If the DTC resets, replace 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