Refer to Antilock Brake System Schematics .
Circuit Description
The PCM receives rough road information from the EBCM / EBTCM on the Class 2 serial data circuit. The PCM uses the rough road information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. The EBCM / EBTCM transmits rough road information based on inputs from the wheel speed sensors. If a loss of communication occurs which causes the PCM not to receive rough road information while DTC P0300 is requesting the MIL, DTC P1381 will set.
Conditions for Running the DTC
| • | Engine load is less than 87 percent. |
| • | Engine speed is less than 5000 RPM. |
| • | Vehicle speed is more than 10 mph. |
| • | A misfire DTC is occurring and requesting the MIL to be illuminated. |
Conditions for Setting the DTC
The PCM is detecting a loss of communication with the EBCM / EBTCM for at least 10 seconds.
Action Taken When the DTC Sets
The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction free warm-up cycles. |
| • | The PCM receives a clear code command from the scan tool. |
Diagnostic Aids
Inspect for the following:
Important: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
Inspect the PCM and the engine grounds for clean and secure connections.
If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Ensures that the EBCM/EBTCM is capable of transmitting serial data on the UART serial data circuit.
-
Tests the UART serial data circuit at the EBCM/EBTCM for correct voltage.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Can ABS data be displayed? | -- | |||
3 | Test the serial data circuit for an open or a faulty connection. Refer to Circuit Testing and Wiring Repairs or Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | System OK | Go to Diagnostic Aids |
Does the voltage vary within the specified range ? | 1-5V | |||
5 | Inspect for a poor connection at the EBTCM. Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
6 | Test for an open in the serial data circuit to the EBTCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Self-Diagnostics in ABS/TCS | |
7 |
Can ABS data be displayed? | -- | System OK |
