For 1990-2009 cars

### System Description

The powertrain control module (PCM) 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 rotation 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 PCM on the serial data circuit. If DTC P0300 is set and the rough road information is not available due to an ABS 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

• | The vehicle speed is above 16 km/h (10 mph).

• | The engine speed is less than 3,200 RPM.

• | The engine load is less than 60 percent.

• | Engine misfire is detected--DTC P0300 set.

• | DTC P1381 runs continuously when the above conditions are met.

### Conditions for Setting the DTC

• | A serial data malfunction exists preventing the PCM from receiving rough road detection data.

• | The above conditions are met for 5 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.

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step will diagnose a malfunction in the serial data circuits.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Does the scan tool display any antilock brake system (ABS) DTCs? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | Go to Symptoms - Antilock Brake System