Circuit Description
The powertrain control module (PCM) supplies approximately 5 volts through an internal resistor to the electronic brake control module (EBCM) on the requested torque signal circuit. The EBCM toggles this voltage to ground in order to create the requested torque signal at the PCM. A signal with a frequency of 128 Hz +/- 5 percent and a duty cycle of 25-95 percent is a valid requested torque signal. The percentage of duty cycle is proportionate to the percentage of requested engine torque.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0241 or DTC P0856 Pulse Width Modulated (PWM) Requested Torque
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The engine is running at a speed greater than 450 RPM for 1 second. |
Conditions for Setting the DTC
C0241
The EBCM receives an invalid requested torque signal for 300 milliseconds.
P0856
The PCM detects open or shorted requested torque signal voltage as being less than 4.75 volts or greater than 5.25 volts.
Action Taken When the DTC Sets
| • | The EBCM disables the vehicle stability enhancement system (VSES). |
| • | The stability indicator turns ON. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
Diagnostic Aids
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:
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? | 5 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 |
Important: Following EBCM replacement, perform the set-up procedure for the EBCM and perform the Yaw Rate Reference Table Reset Procedure. Use the scan tool to perform the Tire Size Calibration procedure. 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 |
