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 illuminates the malfunction indicator lamp (MIL) on
the third consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic
fails. The first time the diagnostic fails, the control module stores this information
in the Failure Records. If the diagnostic reports a failure on the second consecutive
ignition cycle, the control module records the operating conditions at the time
of the failure. The control module writes the operating conditions to the Freeze
Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after
4 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | 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 emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
