P1381

CIRCUIT DESCRIPTION
Rough roads cause torque on the tires that is transmitted to the powertrain. This condition slows down the crankshaft, giving the appearance of a misfire. The electronic brake and traction control module (EBCM) determines rough road surfaces using input from the wheel speed sensors. The EBCM then sends the rough road data to the PCM via class 2 serial data. The powertrain control module (PCM) uses the rough road data in order to enhance the misfire diagnostic. The data allows the PCM to distinguish the crankshaft speed variations caused by rough road surfaces from those caused by true misfires. If a loss of communication occurs that causes the PCM not to receive the rough road information when a misfire condition is requesting the malfunction indicator light (MIL), diagnostic trouble code (DTC) P1381 will set.

CONDITIONS FOR RUNNING THE DTC
^ The engine load is less than 87 percent.
^ Engine speed is less than 5000 RPM.
^ Vehicle speed is more than 16 km/h (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 for approximately 5 seconds or more.

ACTION TAKEN WHEN THE DTC SETS
^ The control module stores the DTC information into memory when the diagnostic runs and fails.
^ The malfunction indicator lamp (MIL) will not illuminate.
^ The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
^ The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC Last Test Failed clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ Clear the DTC with a scan tool.

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter kit J 35616-A Notice in Service Precautions.

If the condition is intermittent, refer to Intermittent Conditions in Symptoms. Intermittent Conditions

TEST DESCRIPTION

Steps 1-2:

The number below refers to the step number on the diagnostic table.
2. This step ensures that the EBCM is capable of transmitting serial data on the class 2 serial data circuit.