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DTC C1255 or C1256

DTC 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 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 is cleared when a diagnostic test is run and passes.

• The DTC in the history is cleared after 40 consecutive fault-free ignition cycles have taken place.


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. Switch ignition ON.

2. Check that DTC C056D or C056E is not generated.

3. If any of the specified DTCs has been triggered, see DTC (DTC) list - vehicles .

4. Replace K17 electronic brake control module.

5. Verify that DTCs C1255 or C1256 are not set when the vehicle is manoeuvred as specified in "Conditions for running of DTCs" above.

6. If any of these DTCs is generated:

7. Replace the control device that set the DTC.

8. If none of these DTCs are generated:

9. All OK.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

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