DTC P1380: EBCM DTC Detected Rough Road Data Unstable: Description

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.

The Powertrain Control Module (PCM) detects engine misfire by detecting variations in crankshaft deceleration between firing strokes. For accurate detection of engine misfire, the PCM must distinguish between crankshaft deceleration caused by an actual misfire and deceleration caused by rough road conditions. The Anti-lock Brake System (ABS) can detect if the vehicle is on a rough road based on the wheel acceleration and deceleration data supplied by the wheel speed sensors. If the ABS detects a rough road above a predetermined threshold, this information is sent to the PCM via serial data. The PCM can then take the rough road into account when calculating a misfire. Even if the ABS is malfunctioning and cannot detect rough roads, the misfire diagnostic will continue to run. However, if a misfire DTC sets, this additional DTC also sets indicating that rough road data was not available during the misfire calculation due to an ABS malfunction.