Electronic Control Engine Diagnostic System Research Based On CAN Bus

Automobile engine diagnosis technology plays a very important role in research of automotive electronic control system, the detection diagnosis and maintenance of vehicles.This thesis analyzes the car diagnosis technology development situation and developing trend of both domestic and foreign,and puts forward the proposal CAN communication circuit module hardware and OBD communications, which will gain CAN frame and transmit information to PC. This paper designs a diagnosis system from diagnosis technology and pc-based diagnostic tool combination of electronic controlled engine diagnosis system. After a detailed study in automotive electronic control technology and single-chip microcomputer technology, the CAN bus technology, CAN bus application protocol and LabVIEW software, the paper establishes the electronic control engine diagnostic system based on CAN bus.Firstly, this paper introduces ELM327 chip, PCA82C250 chip and MAX232 chip, and establishes CAN diagnosis system hardware circuit which realizes the data link layer signal format conversion, message transmission, message disassembly, message re-assembly, error control, flow control.This hardware circuit which builds hardware bridge for diagnosis system completes the communication between the OBD and PC. Then, LabVIEW software is used to design a program which realizes data flow,fault codes'display, preservation and clearance, and constructs the diagnosis terminal panel. Finally, this paper adopts the design of CAN diagnosis system hardware and software to build a diagnosis system test platform for Toyota. The system function is tested and verified and the experimental results are analyzed and summarized.Through constructing electronic-control engine diagnostic system test platform, can not only collect cars diagnosis of data and information, to establish diagnostic system database, but also be for electronic-controlled engine diagnostic system design, the diagnostic tool research and development of other electric control diagnosis system to provide the reference.