Study On Diagnostic System Of Automobile

With the more and more higher requirement of automobile safe,engine oil consume and emission control regulations,the more and more sensor apply in automobile for monitoring status of engine and vehicle.The complexed systems appear in automobile, such as active and passive safe system and engine controlling system.While enhancing the performance of safety,engine power,fuel economical and exhaut emission,the complex and electronic control system take a new challenge to the automobile service.In order to locate the fault quickly,almost all of the control system was equipped with auto-diagnostic function.The self-diagnostic programe can monitor the running situation of the vehicle.When it detect the fault,The ECU will record the fault into the RAM as fault code type,and enable the MIL light to inform the driver.Using the special diagnostic tool,the service person can know the fault code recorded in the ECU and locate the fault position.This paper introduce the designment of one diagnostic system corresponding to the Xiali automobile.In chapter 1,on the base of reference a great deal of literature,introduce the internal and external research status of automobile diagnostic system,research and development methods,up-to-date achievements and developing trends.Considering the service client, the paper determined the main content of the project.In chapter 2,it introduces the respective function of each part in the engine control system,and introduces OBDII's specification.The paper describe the fundamental of two types of diagnostic protocol,including the conversion of the voltage level,the handshake procedure of tester linking to ECU,the timing request between request and reply and the sequence of each function module.At last,it brings forward the function definition of this diagnostic system.In chapter 3,it describs detailedly the hardware circuit of each function module, including mainly the power module,micro-controller system module,Keyboard input module,screen output module and the communication module.The function of power module is providing the running power to the system,using two hierarchy DC/DC converster.The control system module consists of a core chip of MC9S12DP256B,Timing clock generation circuit and reset circuit.The task of the communication module is transmiting the information between tester and ECU.Differing from the K-Line logic voltage level of ECU,the model of SCM is the standard series communication interface.So one voltage convertor,MC33290 is used to resolve this problem in this system.The input module is a keyboard,and the output module is a LCD screen using to display the test result to the user.In chapter 4,the programs are controlled by module design strategy,compiled with Codewarrior integration develop environment.The software program is composed by main module,Enhanced capture module,SCI module,keyboard input module and data display module.The paper described detailedly respective hardware cicuit,working principle and register setup requirement,and introduced the software implement technique.At last,the writer describes one example about this diagnosic system application,and put forward the operation method and the fators should be considered.The study significance of this paper is to make an effective and easy to used diagnostic system which can be used to indirect the service persion.Equipped with the diagnostic system,the service sites can promote their after-market maintenance performance,and help theriselves to set up a good service representation to the customer.By devising the system,we can know about the control fundamental of each engine system,promote the research and development competence.The execution of the project provides a great engineering experience to Tianjin FAW Led.,about automobile electronic reseach and after-market net building.