C0242

DTC C0242 or P0856

Diagnostic Instructions

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



DTC Descriptors
DTC C0242 00
- Engine Control Module (ECM) Indicated TCS Malfunction

DTC P0856 00
- 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

Ignition voltage is greater than 9.6 volts.


Conditions for Setting the DTC

The ECM detects a fault that prevents it from performing a traction control function and sends a serial data message to the EBCM indicating that torque reduction is not allowed.


Action Taken When the DTC Sets

* The EBCM disables the traction control system (TCS) and vehicle stability enhancement system (VSES) for the duration of the ignition cycle.
* The ABS indicator illuminates.
* The Stabilitrak indicator illuminates.
* The driver information center (DIC) displays all wheel drive (AWD) OFF /Service Traction Control/Service Stabilitrak message.



Conditions for Clearing the DTC

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



Diagnostic Aids

These DTCs are an indicator that the ECM receives an invalid message from the EBCM , and does not necessarily indicate a fault is present with the EBCM. This DTC should not be used as a fault indicator, but rather as a symptom to assist in the diagnosis of these other systems.


Reference Information
Schematic Reference

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

Component Connector End Views (Connector Views)
Description and Operation

ABS Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for scan tool information


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) .