Service Information

Volt

DTC C0242 or P0856

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 C0242 00: Powertrain Control Module Indicated Traction Control Malfunction

DTC P0856: Engine Control Module (ECM) Traction Control Torque Request Circuit

The electronic brake control module and the engine control module simultaneously control the traction control. The electronic brake control module sends a serial data message to the engine control module requesting torque reduction. When certain engine control module DTCs are set, the engine control module will not be able to perform the torque reduction for traction control. A serial data message is sent to the electronic brake control module indicating that traction control is not allowed.

Conditions for Running the DTC

•	Vehicle in Service Mode.

•	The ignition voltage is greater than 10 V.

Conditions for Setting the DTC

The engine control module diagnoses a condition preventing the engine control portion of the traction control function and sends a serial data message to the electronic brake control module indicating that torque reduction is not allowed.

Action Taken When the DTC Sets

•	The ABS indicator turns ON.

•	The MIL indicator may be on or flashing.

•	The traction control/stability control indicator turns ON.

•	The Service StabiliTrak message is displayed on the driver information centre.

•	The electronic brake control module disables the antilock brake system, the traction control system and the electronic stability program for the duration of the drive cycle.

Conditions for Clearing the DTC

•	The condition for setting the DTC is no longer present.

•	The history DTC will clear after 40 consecutive fault-free drive cycles have occurred.

Reference Information

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 Verification

Vehicle in Service Mode.
Verify that no other DTCs are set except for C0242 or P0856.

⇒	*If any other DTCs are set*

Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

⇓	*If no other DTCs are set*

Replace the K20 engine control module.
Verify that DTC C0242 or P0856 does not set while operating the vehicle under the Conditions for Running the DTC. You may also operate the vehicle under the conditions that you observed from the Freeze Frame/Failure Records data.

⇒	*If DTC C0242 or P0856 sets*

Replace the K17 electronic brake control module.

⇓	*If DTC C0242 or P0856 does not set*

All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for electronic brake control module or engine control module replacement, programming and setup