DTC P1381: Misfire Detected - No Communications With Brake Control Module: Description

PCM receives rough road information from the Electronic Brake Control Module (EBCM) on the class II serial data circuit. PCM detects engine misfire by detecting variations in crankshaft deceleration between firing strokes. For accurate detection of engine misfire, PCM must be able to distinguish between crankshaft deceleration caused by actual misfire or deceleration caused by rough road conditions.

The ABS system can detect if vehicle is on a rough road based on wheel acceleration/deceleration data supplied by the wheel speed sensors. If ABS system detects rough road greater than a predetermined threshold, this information is sent to the PCM via the serial data (UART). PCM can then take the rough road into account when calculating misfire. Even if the ABS is malfunctioning and cannot detect rough roads, the misfire diagnostic will continue to run.