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 antilock 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 effect 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,
or a serial data malfunction, DTC P1381 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1381 Misfire Detected - No Communication with Brake Control Module
Conditions for Running the DTC
| • | Engine misfire is detected--DTC P0300 is set. |
| • | DTC P1381 runs continuously once the above condition is met. |
Conditions for Setting the DTC
| • | A serial data malfunction exists preventing the ECM from receiving rough
road detection data. |
| • | The above conditions met for 20 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. |
