electronic control unit (ECU) controls microprocessor (CPU), memory (ROM,. RAM), I/O interface 1/, analog-to-digital converter (A/D), shaping, driving and other microcomputer contents, and calculates, processes and judges the information input by air flow meters and various sensors according to the programs and data in its memory, and then outputs instructions to provide certain fuel injectors. The electronic control unit consists of microcomputer, input, output and control circuits. Generally, the voltage working range of ECU is 6.5-16V (with voltage stabilizing devices at key points inside), the working current is .15-.18, and the working temperature is 4-8 degrees below zero. It can bear the vibration below 1Hz, so the probability of ECU damage is very small. The CPU is the core part of ECU, and it has the function of calculation and control. When the engine is running, it collects the signals of various sensors, performs calculation, and converts the calculation results into control signals to control the work of the controlled object. It also controls the memory (RO M, RAM), input/output interface (1/) and other external circuits. The program stored in the memory ROM is based on accurate calculation and a large number of experimental data. When the engine is working, this inherent program is constantly compared and calculated with the signals collected from various sensors. The results of comparison and calculation control the ignition, air-fuel ratio, idle speed, exhaust gas recirculation and other parameters of the engine. It also has the function of fault self-diagnosis and protection. When the system has a fault, it can automatically record the fault code in RAM and take protective measures to read the replacement program from the above-mentioned inherent program to maintain the operation of the engine, so that the car can drive to the repair shop.