Circuit Description

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 engine control module (ECM) via class 2 serial data. The data allows the ECM 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 P0318 will set.