Diagnostic Instructions
DTC Descriptors
DTC C0240: PCM Traction Control Not Allowed
DTC P0856: Traction Control Torque Request Circuit
Circuit/System Description
C0240
The powertrain control module (PCM) and the electronic brake control module (EBCM) communicate on the serial data link, whenever the ignition is ON.
P0856
The PCM supplies 5 volts through an internal resistor, to the EBCM on the requested torque signal circuit. The EBCM toggles this voltage to ground to create a valid requested torque signal at the PCM.
Conditions for Running the DTC
C0240
The ignition is ON.
P0856
| • | The engine is running at a speed greater than 450 RPM for 5-20 seconds. |
Conditions for Setting the DTC
C0240
The EBCM receives a serial data message stating that the PCM has lost the ability to reduce engine torque.
P0856
The PCM receives an invalid requested torque signal for 3 seconds.
Action Taken When the DTC Sets
C0240
| • | The EBCM disables the traction control system (TCS) and vehicle stability enhancement system (VSES). |
| • | The TRACTION FAILED message is displayed. |
| • | The Stability Caution indicator turns ON. |
| • | The DIC displays the SERVICE STAB SYS message. |
P0856
| • | The PCM sends a serial data message to the EBCM stating that the PCM has lost the ability to reduce engine torque. |
| • | The EBCM sets DTC C0240 as a current DTC for as long as the malfunction is present. |
Conditions for Clearing the DTC
C0240
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
P0856
| • | The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function. |
| • | A history DTC clears automatically after 40 consecutive warm-up cycles without a PCM detected failure. |
Diagnostic Aids
C0240
A requested torque signal malfunction is only one possible cause for the PCM to lose the ability to perform traction control. DTC C0240 may set due to engine overheating, throttle actuator control failure, loss of ignition timing control by the
PCM, etc. If DTC P1571 has not set, refer to
Diagnostic System Check - Vehicle
to identify other possible causes of DTC C0240.
P0856
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction.
Reference Information
Schematic Reference
Antilock Brake System Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Testing
- Use a scan tool in order to clear the DTCs. Cycle the ignition to OFF and then start the engine. A current failure will set a DTC.
| ⇒ | If the DTC does not reset, go to Diagnostic Aids. |
- Turn OFF the ignition and disconnect the EBCM harness connector. At the EBCM harness connector, use a DMM to measure for 5 volts on the requested torque circuit. Turn ON the ignition.
| ⇒ | If the voltage is below 4.5 volts, test for an open or short to ground on the requested torque circuit or replace the PCM. |
| ⇒ | If the voltage is above 6 volts, test for a short to power or replace the PCM. |
- Connect one end of a test lamp to ground. With the DMM still connected to the EBCM harness connector, touch the other end of the test lamp to the DMM lead connected to the EBCM harness connector. The DMM voltage reading should drop below 0.5 volt.
| ⇒ | If the voltage does not drop to below 0.5 volt, check for a short to voltage on the requested torque circuit or replace the PCM. |
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for EBCM or PCM replacement, setup, and programming
