In the digital system where safety is a major issue, the reliability issue has been more important. However, as the circuit design has been more complicated, the number of some errors which escaped from the pre-silicon verification has been increased and the undetected errors have a bad influence upon reliability. To solve this problem, an online test and debug methodology for the automotive image processing system is proposed in this paper. Experimental results show the proposed methodology has high system reliability and provides the concurrent operation with a negligible test time and a small hardware overhead compared to the previous works.