When the automobile was first invented, it was a purely mechanical creation. Fast-forward 130 years: Dozens of computers control everything from wiper blades and power windows to the internal combustion engine and transmission. The two main computers we usually worry about are the engine or powertrain control module (ECM or PCM) and the transmission control module (TCM).

Physically, the ECM and TCM may be located anywhere in the vehicle, such as in the trunk, under the dash, or under the hood. Using dozens of sensors, such as those that measure engine coolant temperature or transmission output shaft speed, the ECM monitors engine and transmission function. Using this data, it can fine-tune actua ... Read more »