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 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 ignition is ON.

• | 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

Antilock Brake System Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Scan Tool Data List

### Circuit/System Testing

1. 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.

2. Ignition OFF, disconnect the harness connector at the EBCM.
3. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 23 and ground.

⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage.

4. If the circuits test normal, replace the ECM. If DTC resets, replace the EBCM

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM or PCM replacement, setup, and programming