Circuit Description
The EBCM and the PCM simultaneously control the traction control. The EBCM sends a Requested Torque message via a pulse width modulated (PWM) signal to the PCM. The duty cycle of the signal is used to determine how much engine torque the EBCM is requesting the PCM to deliver. Normal values are between 10 and 90 percent duty cycle. The signal should be at 90 percent when traction control is not active and at lower values during traction control activations. The PCM supplies the pull up voltage that the EBCM switches to ground to create the signal.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C0241 Powertrain Control Module (PCM) Indicated Requested Torque Malfunction |
| • | DTC P0856 Traction Control Torque Request Circuit |
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The PCM diagnoses the requested torque PWM signal circuit and sends a class 2 serial data message to the EBCM indicating a fault is present. A fault exists in the circuit if the PCM detects one of the following conditions:
| • | The requested torque PWM signal is less than 5 percent duty cycle or greater than 95 percent duty cycle. |
| • | The requested torque PWM signal is not present for 10 seconds. |
Action Taken When the DTC Sets
If equipped, the following actions occur:
| • | The electronic brake control module (EBCM) disables the traction control system (TCS)/vehicle stability enhancement system (VSES) for the duration of the ignition cycle. |
| • | A malfunction DTC will set. |
| • | The Stability Off indicator turns ON. |
| • | The antilock brake system (ABS) remains functional. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present (the DTC is not current) and you used the scan tool Clear DTC function. |
| • | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Use the scan tool in order to determine if the requested torque signal has a valid duty cycle.
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Measure the requested torque signal in order to determine if the signal has a valid duty cycle.
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Measure the requested torque signal in order to determine if the signal has a valid frequency.
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This vehicle is equipped with a powertrain control module (PCM) which uses an electrically erasable programmable read only memory (EEPROM). When replacing the PCM, the replacement PCM must be programmed.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 | Inspect the electronic brake control module (EBCM) ground and powertrain control module (PCM) ground, ensuring each ground is clean and torqued to the proper specification. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 3 | ||||
Does the scan tool display less than the specified value? | 100% | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 | |||||
Is the duty cycle within the specified range? | 5-95% | Go to Step 5 | Go to Step 6 | |||||
Measure the DC Hz between the requested torque signal circuit and a good ground. Does the frequency measure within the specified range? | 121-134 Hz | Go to Step 8 | Go to Step 6 | |||||
6 |
Important: Disconnecting the EBCM connector and turning ON the ignition could cause other modules to set loss of communication DTCs (Uxxxx). Once the EBCM is reconnected, the EBCM may set DTC C0241. Does the voltage measure within the specified range? | 4-6 V | Go to Step 10 | Go to Step 7 | ||||
7 |
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||
8 |
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||
9 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||
10 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||
Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 13 | -- | |||||
12 | Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 13 | -- | ||||
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||
