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Nanjing's Fiat km PALIO 1. 5L hatchback with a mileage of about 76 thousand. The car had a traffic accident, but the engine was not damaged, but the appearance damage was serious. After the accident was completed, the engine test was started, but the engine was unable to start the engine. The reason was that there was no high pressure fire. Through further detection, it was found that the crankshaft position sensor was damaged. Then the crankshaft position sensor was replaced, and then the engine was easy to start the engine, but then the following failure occurred: once the cooling fan entered the high speed operation stage, the engine was automatically extinguished. The engine can not start the engine immediately after the extinguishing. It is easy to start the engine when the engine temperature is reduced. When the cooling fan goes into the high speed operation stage, the engine will turn out again. Fault diagnosis: after the maintenance technician receives the vehicle, it first verifies the failure phenomenon. After several tests, it is found that there is a fault. Connecting the X-431 fault detector to diagnose, it is found that the fault diagnosis instrument can not communicate with the engine electronic control unit normally. In desperation, the car can only be analyzed according to the conventional method. When the engine has just been extinguished, immediately pull out a cylinder and plug the spark plug to check if there is a high pressure fire, the engine is in the case of "lack of cylinder" in the case of the machine. Then, after the engine is turned off, insert a cylinder cylinder line and try the fire again. The engine has no indication of the engine, and then pulls out a cylinder high voltage line. Continue to start test, engine can start the machine again. According to these inspection results and combined with the analysis of the failure phenomena, it is considered that the fault is caused by the ignition of a cylinder spark plug at high temperature. When the engine ECU receives a cylinder spark plug fire signal, the protection measures are implemented, so that the fuel injector is no longer injected, so the engine immediately flameout. When the engine temperature drops and the engine is restarted, the spark plug does not lose the fire, and the engine electronic control unit is normal to the injector, so the engine can start the engine again. But after all the 4 spark plugs were replaced, it was found that the above failure still existed, and a strange new failure occurred when the engine was working normally. Some people use the hand to touch the crankshaft position sensor output signal line engine to extinguish, but some people touch the crankshaft position sensor output signal line engine will not be flameout. After consultation, it is agreed that this "strange phenomenon" is the result of static interference, because the size of the resistance of each person is different, the electrostatic voltage is not the same, and the intensity of the interference is not the same. Because the engine crankshaft position sensor is a magnetoelectric structure, it is an AC generator, it is an active signal generator, its signal is weak, only milli voltage level, in order to prevent the sensor from the weak signal is interfered, so the shield line is added, if the shield line is damaged, It is not surprising that the above phenomenon is known. Check the shielding line on the outside of the crankshaft of the crankshaft position sensor, and it is found that there is a broken section at the joint, so it is wrapped and treated to ensure the shielding effect. Then the signal value of the crankshaft position sensor was detected. Using the multimeter AC voltage shift (2V shift) measurement, the output signal is 245mV, the standard value should be no less than 250mV. So the clearance between the crankshaft position sensor and the ring of the signal generator is detected. The measured clearance is 0. 80mm, the standard value should be 0.2 ~ 0. 4mm, so the crankshaft position sensor installation hole is worn out with the grinding wheel to make the gap between the two people reach the standard value. Then the fire test was carried out, and the trouble remained. According to the reference data, the electronic control engine, since the fire can be protected and controlled, also has the memory, although the failure is excluded, but its memory can not disappear immediately, it must be restudied to restore normal working condition. Then decided to drive the car out of the factory for road test, in less than 5 km engine when the engine is flameout several times, but after continuing to drive, the engine auto extinguishing phenomenon has not appeared again. The fault is completely eliminated.