Fault phenomenon: a Santana car has done routine maintenance in a car repair plant, replacing the timing belt and the coolant pump. After the car comes out, the engine sometimes automatically extinguish, and the engine can not start after the engine is extinguished. It needs to wait about 10 min before the engine can start, and the crankshaft has been replaced for this purpose. Position sensor and engine control unit and so on. But the fault still cannot be ruled out. Fault diagnosis and removal: after taking the car, first check the basic engine control unit is the old, the crankshaft position sensor is new; the owner reflected that because the problem still exists, so the original engine control unit has been changed back. The fault of the car is carefully analyzed. It is said that the engine should not be extinguished after conventional maintenance, and the replacement of the crankshaft position sensor and the engine control unit is invalid, indicating that the fault is not caused by these components. Ask the owner of the engine when the engine is out of action, reflecting the sudden extinction. According to the situation reflected by the owner, there is no crew in the engine control unit when there is a fault. It may be the power supply of the engine control unit. After the ignition switch is disconnected, it will be connected again, and the sound of the fuel pump can not be heard. Check the relevant fuse and do not find any abnormal condition. Then check the relay and find that a relay is not on the fuse rack but on one side. The relay was inserted into the relay seat and found that the relay terminal and the relay seat were badly hit, so the relay terminals were repaired with the sharp mouth tongs and then re inserted to test the car. The above failure phenomenon disappeared. After half a month's phone call, the car failed to appear again, and the trouble was completely eliminated.