Research Of Portable Automobile Malfunction Tester Based On OBD-Ⅱ

With the Electronic Control System of modern engine being more and more complex,once there is any breakdown in the automobile,it will be more and more difficult to confirm the type of the trouble. So the automobile malfunction tester has been the indispensable equipment during repairing.However,the traditional OEM tester has many drawbacks,such as high price,poor versatility and not easy to carry etc.The paper developed the Portable Automobile Malfunction Tester based on OBD-Ⅱ(hereinafter OBD2 tester),and the OBD2 tester has solved the problems above efficiently.The OBD2 tester,which is based on OBD-Ⅱstandards,adopts MCU as the main control device,employs SAE J1979 as diagnostic protocol, and uses ISO 9141-2 as communication protocol.When linked with the automobile Electronic Control Unit,the OBD2 tester can read and clear the DTC.The circuit conversion module between MCU serial port and serial interface of RS-232 has been added to the hardware circuit of OBD2 tester.When connected with PC,the OBD2 tester will upload the DTC data.We could develop the automobile-malfunction-diagnostic Expert Systembased on PC,which possesses powerful data-processing and applied-program-developing functions,to further analyze DTC data.The thesis analyzed the OBD2 tester's hardware and software, and meanwhile demonstrated its advantages,such as low price,high dependability,easy to carry,easy to use and easy to be expanded and so on.Especially,the repairman could easily read and clear DTC even being outdoors due to the portable design.The article highlighted the components selection of the OBD2 tester and adoption Integrated Development Environment,that is Protel DXP 2004 SP2,to design schematics and PCB.On the other hand,the paper detailed employing IDE KeilμVision2 to develop monitoring program and communication program based on OBD-Ⅱstandards.The article described the difficulties and focuses in design,and detailed the realization of the OBD2 tester.The OBD2 tester has past the function experimentation in automobile repair shop,and the experiment approved the instrument has a high performance in malfunction diagnosis.In particular,the OBD2 tester is fit for common driver or maintenance personnel to carry through daily examination and malfunction finding.