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A 2007 Chery Rui tiger, carrying the SQR481 engine, matching the QR523 manual transmission, the user reflects that the car has changed the timing belt in other repair plants, the engine fault warning light has been lighted, and the engine speed can not exceed 4000r/min when accelerating. After receiving the car, it is determined that it is exactly as described by the user. The maintenance personnel first connect the fault diagnosis instrument to the engine control system, and the equipment shows that the engine control unit is stored in the fault code "P0341 - the camshaft position sensor signal is not correct". According to our experience in the maintenance of the car, in the control strategy of the engine control system of the car, when the camshaft position sensor fails, the engine will have difficulty in starting and the fault symptoms of the maximum engine speed exceeding 4000r/min, and the engine control unit will store the fault code P0341. After comparison, it is found that the failure symptoms of the camshaft position sensor are completely consistent with the fault symptoms of the vehicle. After that, the operation of the fault code was carried out, but as long as the engine was moved together, the fault code would appear again, indicating that the fault code was the real fault. The reasons for this fault code are: incorrect timing of gas distribution (the relative position of crankshaft and camshaft is incorrect), fault of camshaft position sensor line, fault of camshaft position sensor itself, incorrect position of signal target wheel and internal obstacle of engine control unit. Since the car is defective after replacing the timing belt, I suspect that the timing timing mechanism of the engine is not properly assembled. So the author first used the standard operation specification to re calibrate the timing of gas distribution with special tools, but the engine fault warning lamp could not be extinguished. Referring to the relevant circuit diagrams, the 3 lines of the camshaft position sensor are ground wire, 12V power supply line and signal line respectively. After using the multimeter to measure, the power, grounding and signal lines of the sensor are normal, and there is no break, short circuit and virtual connection. According to the principle of simplicity to complexity, the author first tried camshaft position sensor, but it had no effect. Since the possibility of damage to the engine control unit is relatively small, it has not been replaced. After assembling the timing tool, look at the position of the target wheel, and feel that there are some anomalies in the position of the target wheel. Due to the interference fit between the target wheel and the intake cam, the exact position was not noticed before. In order to determine whether the target position of the vehicle is correct, the author found a comparison of the same vehicle. After installing the timing tool, it is found that the position of the target wheel is about 90 degrees. At this point, it can be determined that the malfunction of the vehicle is caused by the change of the position of the camshaft position sensor. After replacing the intake camshaft assembly and eliminating the fault code with the fault diagnosis instrument, the engine speed of the trial run can reach about 6000r/min, and the trouble is completely eliminated. Summary: the position sensor wheel and camshaft are interference fit, and no change of position will occur in general. The change of the position of the camshaft position sensor of the car can be caused by the correction of the correct time when the repair plant is in school to pry the target wheel with a cone to correct the correct time. The front end of the car's intake and exhaust camshaft has a six square neck with a 24mm open wrench, which can only be realized if the camshaft is needed to turn the camshaft after the timing is removed. Other operations may have adverse consequences, and hope that the maintenance colleagues will pay attention to them.