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.
-
This step tests for voltage supplied to the PCM from the EBCM.
-
This step tests for a shorted resistor in the EBCM or a short to voltage within the circuit, by verifying that a large voltage drop occurs in the circuit when the test lamp is placed in parallel with the DMM. The PCM may be damaged if either of these conditions is present.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | ||||
1 | Did you performs the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the DTC set? | -- | Go to Step 3 | Go to Diagnostic Aids |
Does the voltage measure greater than the specified value? | 4-6 V | Go to Step 4 | Go to Step 5 | |
Does the voltage measure less than the specified value? | 0.15 V | Go to Step 6 | Go to Step 9 | |
5 | Test the requested torque signal circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 |
6 |
Does the scan tool display a duty cycle of the requested torque signal within the specified range? | 25-95% | Go to Step 7 | Go to Step 10 |
7 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 |
8 | Replace the EBCM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 12 | -- |
9 | Test the requested torque signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
11 |
Important: Perform the setup procedure for the PCM. Replace the PCM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
