System Description
The engine control module (ECM) detects engine misfire events by monitoring
variations in the crankshaft rotation speed. Wheel speed changes caused by rough road
conditions can cause changes in crankshaft speed. By monitoring the wheel speed sensors,
the anti-lock brake system (ABS) can determine if the vehicle is operating on a rough
road. If the ABS is detecting a rough road condition severe enough to affect misfire
detection, a rough road signal is sent to the ECM on the serial data circuit. If DTC P0300
is set and the rough road information is not available due to an ABS malfunction,
DTC P1380 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1380 Misfire Detected - Rough Road Data Not Available
Conditions for Running the DTC
| • | The engine is operating for more than 10 seconds. |
| • | DTC P1380 runs continuously once the above condition is met. |
Conditions for Setting the DTC
| • | The ECM does not receive rough road detection data from the EBCM for more
than 2 seconds. |
| • | The above condition is met for 2 seconds. |
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. |
