Circuit Description
The powertrain control module (PCM) receives rough road information
from the electronic brake control module (EBCM) or the electronic brake and
traction control module (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 or EBTCM transmits rough road information
based on inputs from the wheel speed sensors. If the EBCM or EBTCM
detects a condition which will not allow it to properly identify
rough road situations while a misfire condition is being detected
by the PCM, DTC P1380 will be 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 10 mph. |
| • | A misfire diagnostic trouble code (DTC) is occurring, and is requesting
the malfunction indicator lamp (MIL) to be illuminated. |
Conditions for Setting the DTC
The PCM has detected an EBCM or EBTCM rough road sensing error.
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
If DTC P1380 is set, the antilock brake system (ABS) and/or traction
control system (TCS) has detected a malfunction which is preventing the
EBCM or EBTCM from transmitting correct rough road data to the
PCM. Refer to
Diagnostic Starting Point - Antilock Brake System
in Antilock Brake System.
