Study On Diagnosis System For EFI Engine

With the development of the electronics, the electronic controlling technologies are widely used in many parts of automobiles, especially in the engines controlling. Since the rules for emission and fuel consumption are becoming more and more strict, the traditional engines with carburetors can not meet the requirements any longer, and are being replaced by the engines with the electronic control system which comes up with the diagnostic problems. The traditional trouble concepts, serving and diagnostication are out of date, so the paper is focused on the research of the EFI(electronic fuel injection) diagnostic system. The electronic control system of the EFI engine mainly consists of sensors, ECU and executors. The application of the high performance MCU in the ECUs makes it possible and effective the EFI engines' automatic fault diagnosis. The diagnostic system in the paper is based on ECU automatic diagnostic ability. It reads the data, such as the working parameters and error codes, from the ECU , transmits them to the diagnostic center, gets the analytic results from the diagnostic center, and then feeds back to the ECU.The diagnostic system consists of two parts:data-transmitting device and diagnostic center. The data-transmitting agency based on the principle of fax realizes long-distance data transmitting by the public phone net. It uses MCU to control the modules of modem, phone interface and diagnostic center interface to exchange information with the diagnostic center. This device can transmit data in audio mode as soon as it is connected with the phone line. It is able to diagnosticate the engine in real time without human beings participating, which increases the analytic reliability and accuracy and reduces the requirements for maintenance men. It can not only transmit data in long-distance but also inspect in short-distance. The diagnostic center is an applying program platform using VB based on the PC. It receives signals from the data-transmitting device through the serial port, and shows the results or sends out the control order after it deals with the data and makes a judgment. The system can realize the real-time on-line diagnosis for EFI engines, reducing the diagnostic cost and making the fault-diagnosis more quick and convenient. This will favor the popularization of EFI technology.