DTC P1381: Misfire Detected - No EBCM/Pcm Serial Data: Description

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

Rough roads cause torque on the tires that is transmitted to the powertrain. This slows down the crankshaft giving the appearance of a misfire. The Electronic Brake Control Module (EBCM) determines rough road surfaces using input from the wheel speed sensors. The EBCM then sends the rough road data to the Powertrain Control Module (PCM) via class 2 serial data. The PCM uses the rough road data to enhance the misfire diagnostic. The data allows the PCM to distinguish the crankshaft speed variations caused by rough road surfaces from those caused by true misfires. If a loss of communication occurs that causes the PCM not to receive rough road information while a misfire condition is requesting the Malfunction Indicator Lamp (MIL), DTC P1381 will set.