ECU (Electronic Control Unit), also known as "trip computer" and "vehicle computer". Like an ordinary computer, it consists of a microcontroller (MCU), a memory (ROM, RAM), an input/output interface (I/O), an analog-to-digital converter (A/D) and a large-scale integrated circuit such as shaping and driving. In general, the voltage working range of ECU is 6.5- 16V (internal key points have voltage regulators), the working current is 0.0 15-0. 1A, and the working temperature is -40℃~80℃. It can withstand the vibration below 1000Hz, so the probability of ECU damage is very small. CPU is the core part of ECU, which has the functions of calculation and control. When the engine is running, the signals of various sensors are collected and calculated, and the calculation results are converted into control signals to control the work of the controlled object. It also controls memory (ROM/FLASH/EEPROM, RAM), input/output interface (I/O) and other external circuits. The program stored in ROM is written on the basis of accurate calculation and a large number of experimental data. This inherent program is constantly compared and calculated with the signals collected from various sensors when the engine is working. The comparison and calculation results are used to control the ignition, air-fuel ratio, idle speed, exhaust gas recirculation and other parameters of the engine.