Circuit Description
The powertrain control module (PCM) receives rough road information
from the electronic brake control module/electronic brake and traction control
module (EBCM/EBTCM) on the 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/EBTCM transmits
rough road information based on inputs from the wheel speed sensors.
If the EBCM/EBTCM detects a condition which will not allow rough
road situations to be identified 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 5000 RPM. |
| • | The vehicle speed is greater than 16 km/h (10 mph). |
| • | A misfire DTC is occurring and requesting the malfunction indicator
lamp (MIL) to be illuminated. |
Conditions for Setting the DTC
The PCM has detected a EBCM/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
DTC P1380 set indicates that the anti-lock brake system (ABS)
system has detected a malfunction which will not allow the EBCM/EBTCM to transmit
correct rough road data to the PCM. The
Diagnostic System Check - ABS
in Antilock Brake Systems should be used
to diagnose this condition.
