P0856

DTC P0856

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0856 00

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Traction Control Torque Request Circuit Malfunction

Circuit/System Description

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 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 torque reduction is not allowed.

Conditions for Running the DTC

Engine running

Conditions for Setting the DTC

The engine control module detects a fault that prevents it from performing a the torque reduction request 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 electronic brake control module disables the traction control and stability control for the duration of the ignition cycle.

* The traction/stability control indicator turns ON.

Conditions for Clearing the DTC

* 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.

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

Reference Information

Schematic Reference

Antilock Brake System Schematics [1][2]Antilock Brakes / Traction Control Systems

Connector End View Reference

Component Connector End Views Sunshade - Left

Description and Operation

ABS Description and Operation Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Programming and Relearning for scan tool information

Circuit/System Verification

1. With a scan tool record all current DTCs.

2. Diagnosis all other DTCs first starting with U codes, refer to the Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

3. After all of the other DTCs are repaired, verify that DTC P0856 is not set.

• If the DTC is set

1. Replace the K20 engine control module.

2. Operate the vehicle under the conditions for setting the DTC, the DTC should not set.

• If the DTC sets, replace the K17 electronic brake control module.

• If the DTC does not set.

3. All OK.

• If the DTC is not set

4. All OK.

Repair Instructions

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

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