Circuit 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.
DTC Descriptors
This diagnostic procedure supports the following DTC:
| • | DTC C0242:71 ECM Indicated TCS Malfunction |
| • | DTC P0856 Traction Control Torque Request Circuit |
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.
Action Taken When the 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.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | |
