DTC C0242 or P0856. Buick Lucerne 2007

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2007 🢒 Lucerne 🢒 DTC 🢒 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 Descriptor

DTC C0242 00, 71, 75: Engine Control Module (ECM) Indicated TCS Malfunction

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

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.

Actions Taken When DTC Sets

•	The EBCM disables the TCS for the duration of the ignition cycle.

•	The Traction Off indicator turns ON.

•	The message center displays the Service Traction System 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.

Diagnostic Aids

This DTC is for information only. As an aid to the technician, this DTC indicates that there are no problems in the ABS/TCS system.

Reference Information

Electrical Information Reference

•	Testing for Intermittent Conditions and Poor Connections

•	Circuit Testing

Scan Tool Reference

•	Scan Tool Data Definitions

•	Scan Tool Output Controls

Circuit/System Verification

Verify that there are no DTCs set in the ECM.

⇒	If there are any DTCs set in the ECM, diagnose those DTCs.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References