Abstract:The reliability of the system is closely related to testability. A good testability design can improve the reliability of the system. A reliable system is not tested by the final test results, but testability is considered in the design, which has a great impact on the basic reliability of the system. In order to find the optimal vehicle emission control system test, the reliability and testability of the two associated in-depth study, through the system design of the early structure testability analysis, establish system signal flow graph model, the system of the correlation matrix, and the system parameters such as fault detection rate and fault isolation rate analysis. Is proposed based on test coverage of the genetic algorithm for the optimal selection of test items found through this method the experimental simulation system of optimal test item, successfully meet the system fault detection rate and fault isolation rate requirement, the improved genetic algorithm were compared with the traditional genetic algorithm, the improved algorithm has better convergence and better for system analysis.