DTC P1380: Misfire Detected - Rough Road Data Not Available: Description
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 Pontiac Grand Prix, 2002 Pontiac Bonneville, 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, and 2002 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
Powertrain Control Module (PCM) receives rough road information from Electronic Brake Control Module (EBCM) on serial data circuit. PCM uses rough road information to enhance misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. EBCM transmits rough road information based on inputs from the wheel speed sensors. DTC sets when EBCM detects a condition which will not allow EBCM to properly identify rough road situations while a misfire condition is being detected by PCM.