Circuit Description
Rough roads cause torque on the tires that is transmitted to the powertrain. This 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 PCM uses the rough road data 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 rough road information while a misfire condition is requesting the MIL, DTC P1381 will set.
Conditions for Running the DTC
| • | Engine load is less than 52 percent. |
| • | Engine speed is less than 3000 RPM. |
| • | Vehicle speed is more than 5 km/h (3 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 at least 5 seconds.
Action Taken When the DTC Sets
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store the conditions present when the DTC set as Failure Records data only. |
Conditions for Clearing the MIL/DTC
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear DTC Information function. |
Diagnostic Aids
If the condition is intermittent, refer to Intermittent Conditions in Symptoms.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to DTC U1001-U1254 Loss of XXX Communications in Data Link Communications |
