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
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 |
Using this kit will prevent damage caused by the improper probing of
connector terminals.
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.
-
This step ensures
that the EBCM is capable of transmitting serial data on the class 2
serial data circuit.