This paper introduces the application of Kvaser Leaf Light v2 tool in the calibration of a passenger car engine controller(ECU).The performance of the engine directly affects the power output,fuel efficiency and smooth operation of the car,and the engine is the core component of the car;The engine controller(ECU)can control the operation of the engine under various working conditions,ensure that the car reaches the best state under various working conditions,and achieve better fuel saving effect and better running state.