DescriptionAnalog fault simulation is used to make sure that safety mechanism of the analog designs works properly with faults injected into circuits. It can be also used to calculate metric values such as SPFM (Single Point Fault Metric) in order for automotive products to be certificated for ISO26262. Generally, shorts and opens of devices are used as fault models when doing analog fault simulation. In this work, we present the necessity of customizing fault models suitable to automotive sensor designs through experiments because we have noticed that open faults with the big resistance or capacitance can be differently dealt with by each different simulator. In addition, we introduce the way to find weak points of safety mechanism and make the safety mechanism detect specific faulty behaviors of the functional block by investigating the results of fault simulations and finding the tendency of analog circuits’ failure. Analog fault simulation requires an enormous number of simulations because each individual simulation should be executed with each fault, which takes a lot longer time. Therefore, we introduce weighted random sampling method that we have used to get quick results with 95% confidence level in the early design stage.