P0856

DTC C0242 or P0856

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach. Initial Inspection and Diagnostic Overview
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC C0242
- Engine Control Module (ECM) Indicated TCS Malfunction

DTC P0856
- Engine Control Module (ECM) Indicated TCS Malfunction

Circuit/System Description

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

Conditions for Running the DTC

* The ignition is ON.
* Ignition voltage is greater than 8 volts.

Conditions for Setting the DTC

The ECM diagnoses a condition preventing the engine control portion of the traction control function and sends a serial data message to the EBCM indicating that torque reduction is not allowed. The ECM will typically set a DTC and the EBCM will set this DTC.

Action Taken When the DTC Sets

* The EBCM disables the TCS for the duration of the ignition cycle.
* The Traction Off indicator turns ON.
* The DIC displays the Service Traction Control message.
* The ABS remains functional.

Conditions for Clearing the DTC

* The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
* The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Circuit/System Verification

Verify that no DTCs are set in the ECM.

If DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code Descriptions

Repair Instructions

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

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