• 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.

When traction control is active, the electronic brake control module sends a serial data message to the engine control module requesting torque reduction. When certain electronic brake 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.

Engine running.

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

• The traction/stability control indicator turns ON.
• The electronic brake control module disables the traction control and stability control for the duration of the ignition cycle.

• A current DTC clears when the diagnostic runs and passes.
• The electronic brake control module will turn OFF the indicator in the next ignition cycle.

Antilock Brake System Schematics

Master Electrical Component List

ABS Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Verify that no other DTCs are set except for P0856.
• If any other DTCs are set

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

• If only DTC P0856 is set
2. Replace the K20 Engine Control Module.
3. Verify the DTC does not set while operating the vehicle within the Conditions for Running the DTC.
• If DTC sets

  Replace the K17 Electronic Brake Control Module.

• If DTC does not set
4. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

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