For 1990-2009 cars

### 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 Descriptors

DTC P0856: Traction Control Torque Request Circuit

### Circuit/System Description

The electronic brake control module (EBCM) and the engine control module (ECM) simultaneously control the traction control. The ECM reduces the amount of torque supplied to the drive wheels and the EBCM actively applies the brakes to the front wheels in order to reduce torque. The EBCM sends a GMLAN serial data message to the engine control module (ECM) indicating the function that has been requested.

### Conditions for Running the DTC

• | The ignition is ON.

• | The DTCs run continuously once the above condition is met.

### Conditions for Setting the DTC

The ECM detects an invalid signal from the EBCM.

### Action Taken When the DTC Sets

DTC P0856 is a Type C DTC.

### Conditions for Clearing the DTC

DTC P0856 is a Type C DTC.

### Reference Information

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

### Circuit/System Verification

1. Observe the Freeze Frame/Failure Records with a scan tool.
2. Clear the DTCs with a scan tool.
3. Ignition OFF for 30 seconds.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

⇒ | If DTC P0856 failed this ignition, replace the EBCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup, and programming.