Circuit Description
The electronic brake control module (EBCM) and the powertrain control module (PCM) simultaneously control the Traction Control System (TCS). 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 engine is running.
Conditions for Setting the DTC
C0241
The EBCM has detected an open, short to power or short to ground on the requested torque signal circuit.
P0856
One of the following conditions exists:
| • | The PCM detects that requested torque signal is out of the valid range. |
| • | The PCM does not receive the requested torque signal. |
Action Taken When the DTC Sets
When the DTC sets the TCS can not reduce engine torque, however the brake intervention portion of the TCS System remains operational.
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present 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. |
| • | The PCM automatically clears the history DTC when a current DTC is not detected in 40 consecutive warm-up cycles. |
Diagnostic Aids
Check for poor or intermittent connections of the EBCM and the PCM. Refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for voltage supplied to the EBCM from the PCM.
-
This step tests for a shorted resistor in the PCM or a short to voltage within the requested torque signal circuit by verifying that a large voltage drop occurs when a test lamp is connected in parallel with the DMM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Is DTC P0856 set? | -- | Go to Step 3 | Go to Diagnostic Aids |
3 |
Does DTC P0856 set? | -- | Go to Step 4 | Go to Diagnostic Aids |
Does the voltage measure greater than the specified value? | 4.75 V | Go to Step 5 | Go to Step 6 | |
Does the voltage measure less than the specified value? | 0.15 V | Go to Step 9 | Go to Step 7 | |
6 | 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 8 |
7 | 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 10 |
8 | Inspect for poor connections at the harness connector of the powertrain control module (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 10 |
9 | Inspect for poor connections at the harness connector of the EBCM. 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 |
10 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the EBCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does DTC P0856 reset? | -- | Go to Step 4 | System OK |
