C0256

DTC C0256, C12E6, or C12E7

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 Instructionsprovides an overview of each diagnostic category.

DTC Descriptors
DTC C0256 04
- Valve Relay Contact Circuit Open

DTC C12E6
- ABS Switch Circuit Open

DTC C0256 0E
- Valve Relay Contact Circuit Resistance Below Threshold

DTC C12E7
- ABS Switch Circuit Shorted

Circuit/System Description

The base brake solenoid relay, located within the electronic brake control module (EBCM), supplies battery voltage to all of the valve solenoids.

Conditions for Running the DTC

* Ignition ON.
* The ignition voltage is greater than 10 volts.

Conditions for Setting the DTC

C0256 04 or C12E6
* The EBCM detects an open in the circuits to the solenoid valve relay.
* The EBCM detects a stuck open solenoid valve relay.

C0256 0E or C12E7
* The EBCM detects an short to battery in the circuits to the solenoid valve relay.
* The EBCM detects a stuck closed solenoid valve relay.

Action Taken When the DTC Sets

* The EBCM disables the antilock brake system (ABS) and the vehicle stability enhancement system (VSES) 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 [1][2]Antilock Brakes / Traction Control Systems
Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1 A4
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 Control Module Referencesfor scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the K17 EBCM.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 ohm between the ground circuits listed below and ground:

* Terminal 13
* Terminal 38

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuits listed below and ground.

* Terminal 1
* Terminal 25

• If the test lamp does not illuminate, test the appropriate circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, replace the Q5 brake pressure modulator valve assembly.

4. If all circuits test normal, replace the Q5 brake pressure modulator valve assembly and verify DTC does not reset. If the DTC resets, replace the K17 EBCM.

Repair Instructions

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

* Electronic Brake Control Module with Brake Pressure Modulator Valve Replacement Electronic Brake Control Module with Brake Pressure Modulator Valve Replacement
* Control Module References Control Module Referencesfor EBCM replacement, programming and setup