The Research And Development Of Vehicle Fault Diagnostic System Based On MDI

Increasingly stringent emission regulations and further requirements about ve-hicle performance, which puts forward higher requirements for the vehicle fault de-tection. Currently, lack of functional and standardized about vehicle fault diagnosticsystem results in low efficiency, long development cycle and high cost. Through ana-lyzing vehicle communication protocols and designing vehicle bus system functionalrequirements of vehicle fault diagnostic system, this paper presents a PC-style vehiclefault diagnostic system design based on standards diagnostic interface device MDI.The main research and development to the following:Firstly, the vehicle bus system is divided into the physical layer, data link layer,transport layer and application layer, respectively analyzes mainstream communica-tion protocol, including the data link layer protocol ISO9141and ISO14230basedon K-line, data link layer protocol ISO11898based on the CAN bus, transport pro-tocol ISO15765-2based on CAN bus and application layer diagnostic protocolKWP2000.Secondly, this paper designs the overall system solution. Based on the analysisof the system functional requirements, designs the overall system architecture anddevelopment process. According to the versatility, scalability and standardization re-quirements for system hardware, selects standards diagnostic interface device and PC,and studies SAE J2534standard for standards diagnostic interface device MDI.Thirdly, according to the vehicle bus communication protocol and SAE J2534protocol analysis, from the establishment of the communication process and the op-timization of the communication rate, this paper studies the system communicationmechanism to meet the system reads the data accuracy and real-time requirements, onthis basis, using the development ideas of hierarchical architecture and functionalmodular, develops the vehicle fault diagnostic system software and data flow graphplayback management software.Finally, this paper tests the main function of the system and analyzes the results,the main functions including fault diagnosis function, electronic control module re-fresh function, automatic update function and curves playback function. Through real vehicle testing and analysis, this system reads data with high accuracy, fast response,meets not only the basic diagnostic tasks, but also real-time monitoring of vehiclesand engine operating conditions, in addition, this system has online refresh function,vehicle maintenance help function and data flow graph playback function, provides apowerful tool and technical support for vehicle’s diagnosis and repair.