DTC C123C, C1255, or C1256

 Diagnostic Instructions


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

 DTC C123C 00

Electronic Brake Control Module RAM Malfunction

 DTC C1255 00

Electronic Control Unit Performance Malfunction

 DTC C1256 00

Control Module Programming Checksum Error Malfunction

 Circuit/System Description

When the ignition is turned ON, the microprocessor runs a diagnostic program to detect an internal fault when power up is commanded. If an internal malfunction is detected, the control module will set a DTC.

 Conditions for Running the DTC

Ignition ON

 Conditions for Setting the DTC

The control module detects an internal malfunction.

  Action Taken When the DTC Sets

Specific subsystems will not function or operate in degraded mode.

 Conditions for Clearing the DTC

A current DTC clears when the diagnostic runs and passes.

 Reference Information

 Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

 Circuit/System Testing


1. Ignition ON, verify that DTC C0569, C056D, or C056E is not present in the electronic brake control module (EBCM).

2. If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC prior to this diagnostic.
3. Replace the K17 Electronic Brake Control Module and verify the DTC does not reset.
4. If the DTC resets, replace the module that set the DTC.
 Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

 Control Module References for module replacement, setup and programming