Abstract: With the rapid development of automotive electronics and information technology, automotive intelligence and safety have been further improved.The current situation of Passive entry system is commonly configured in middle and high-end models which makes the operation of the car more convenient and the anti-theft function more powerful and has become a typical representative of the intelligent upgrading of the body of automobile.However, with the popularization of the Passive entry system, the traditional automobile maintenance enterprises still have technical limitations in troubleshooting of the system.This article takes the Magotan B8L as an example to thoroughly sort out the fault mechanism, use fault tree analysis to deeply analyze the cause of the fault, summarize the impact of the probability of basic events on the entire system.Based on research, the effect of the current probability of basic events on the whole system is summarized, the qualitative and quantitative analysis is completed, and the strategy of fault diagnosis and removal is introduced with examples.