the electronic control system of automobile engine is called ECU, and in Ford it is called PCM and TCM, in which PCM is dedicated to the control of power output and TCM is used for the conversion control of automatic gearbox. PCM will receive sensor signals, and control the fuel supply, air distribution (electronic throttle), timing of fuel injection and ignition, adjustment of intake pressure through complicated calculations, and determine the compensation control coefficient of the engine according to temperature, load, knock and combustion conditions.

PCM is the current digital transmission system which adopts the Pulse Code Modulation system. PCM was not originally used to transmit computer data, but to make a trunk line between switches instead of just transmitting a telephone signal. PCM has two standards, E1 and T1.

ECU(Electronic Control Unit) electronic control unit, also known as "trip computer" and "vehicle computer". In terms of use, it is a special microcomputer controller for automobiles. Like an ordinary computer, it consists of microprocessor (CPU), memory (ROM, RAM), input/output interface (I/O), analog-to-digital converter (A/D) and large-scale integrated circuits such as shaping and driving. To describe it in a simple sentence is "ECU is the brain of a car".