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

Powertrain Control Module (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.

ABS system can detect if vehicle is on a rough road based on wheel acceleration/deceleration data supplied by wheel speed sensors. If ABS system detects rough road greater than a predetermined threshold, this information is sent to PCM via serial data. PCM can then take rough road into account when calculating misfire. Even if ABS is malfunctioning and cannot detect rough roads, misfire diagnostic will continue to run. However, if a misfire DTC is set, this additional DTC will also set indicating that rough road data was not available during misfire calculation due to ABS system malfunction.