For 1990-2009 cars only
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: Engine Control Module (ECM) Traction Control Torque Request CircuitCircuit/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 ON. |
| • | The ignition voltage is greater than 10 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.
Action Taken When the DTC Sets
| • | The EBCM disables the traction control for the duration of the ignition cycle. |
| • | A DIC message and/or a warning indicator may be displayed. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present. |
| • | The EBCM clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles. |
Reference Information
Schematic Reference
Antilock Brake System Schematics
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Verify that there are no DTCs set in the ECM.
| ⇒ | If there are any DTCs set in the ECM, refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
