The method of automobile ecu is to use reading and writing tools to reload the modified data into the system. Ecu refers to a vehicle-mounted computer, which consists of a microprocessor, a memory, an input/output interface, an analog-to-digital converter, a shaper and a driver. The function of ecu is to calculate, process and judge the information input by air flowmeter and various sensors according to the programs and data in its memory, and then output instructions to provide electric pulse signals with a certain width to the fuel injector to control the fuel injection quantity. Ecu has the functions of fault self-diagnosis and protection. When the system fails, the fault code can be automatically recorded in ram, and protective measures can be taken to read the replacement program from the above-mentioned inherent program to maintain the engine running.