Development of a PC-based OBDII Diagnostic Systemfor Vehicles

• Main Authors: Ming-Jie Xie, 謝明傑
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/xq449y

碩士 === 國立虎尾科技大學 === 動力機械工程研究所 === 93 === Abstract OBD II (On-Board Diagnostics II) is a standard message codes and communication method commonly used in the engine computers of the present vehicles. Its main function is for diagnostic. As the vehicle network system become more sophisticated and advanced, CAN (Controller Area Network) and LIN (Local Interconnect Network) have become the common systems for the engine system to communicate and share information with the other system such as transmission, chassis, car body and safety system. Furthermore, their functions have been extended and include diagnostics as well as control and safety etc. However, even though the hardware structure of communication protocol. Keep renovating and improving, the corresponding message contents and fault codes are still based on the standard protocol of OBD II. This thesis presents an OBD II PC-based diagnostic system for vehicle comprised of an OBD II communication interface and a fault diagnostic program. The former is allowed to communication with some specific type of OBD II engine computers whose physical layer and data link layer are constructed according to ISO 9141 and 9141-2; whose application layer is built based on SAE-J1979; whose fault codes are written by SAE-J2012; whose communication with PC is through RS-232. The latter program used for transmitting receiving and interpreting messages is written in Visual C++. Using this system, the related data and fault codes of the engine in running mode can be obtained. Furthermore, the fuzzy theory is applied to construct an intelligent diagnostic algorithm for this system. Therefore, the specific fuzzy relation matrix of faults for each vehicle can be established using this algorithm. It is highly expected that the proposed system will be an useful tool for vehicle repairmen.