C1256

DTC C1255 or C1256

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 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

* The DTC clears when the diagnostic runs and passes.
* The history DTC will clear after 40 consecutive fault-free ignition cycles have occurred.

Reference Information
Schematic Reference

Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems
Connector End View Reference

Component Connector End Views Connector End Views By Name
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 References for scan tool information

Circuit/System Testing

1. Ignition ON.
2. Verify that DTC C056D or C056E is not set.

• If either DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

3. Replace the K17 electronic brake control module.
4. Verify DTC C1255 or C1256 does not set while operating the vehicle under the Conditions for Running the DTC.

• If either DTC sets
Replace the module that set the DTC

• If either DTC does not set

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

Control Module References Control Module References for module replacement, programming and setup