Throttle opening sensor, crankshaft speed sensor, oxygen sensor, crankshaft position sensor, camshaft position sensor, intake air temperature sensor, water temperature sensor, knock sensor are the most basic sensors in a car engine. Sensors are everywhere. They are responsible for collecting relevant information and sending it to the ECU in the form of electrical signals. After the analog-to-digital converter A/D is converted into a digital signal, the ECU can determine the working state of the engine at this time through calculation. This is the “thinking” process of the ECU. And what is the standard for the “thinking” process? Of course, computers do not have thinking, what is needed is the program stored in ROM. This is equivalent to a piece of software. When the data is transmitted to the ECU, the data in the ROM program is compared with the collected signal, and the ECU obtains the adjustment method. This set of programs is the soul of the ECU. The programming of this program is based on a large number of experimental data, and it often needs to go through bench tests and road tests before it can be established. Usually, refitters change the ECU program by rewriting or revising the ROM program to change the ECU’s operating principles.