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 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
| • | The engine load is less than 87 percent. |
| • | The engine speed is less than 5,000 RPM. |
| • | The 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
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
| • | The PCM harness connectors |
| • | The electrical center fuse/relay cavities |
| • | The component terminals |
| • | The component harness connector |
If the condition is intermittent, refer to
Intermittent Conditions
.
Test Description
The number below refers to the step number on the diagnostic table.
-
This step ensures
that the EBCM is capable of transmitting serial data on the Class 2 serial
data circuit.
