The mileage is over 460 thousand km, and the model is E60, the BMW 535i car equipped with M54 engine in 2003. Users reflect: the car engine jitter. Inspection and analysis: the maintenance personnel detected the engine control unit and found that there was an unreliable fault indication for the exhaust camshaft position sensor signal. According to the inspection plan, no problems were found in the wiring harness, and the power supply and the grounding were normal. Measure the signal waveform of the exhaust camshaft position sensor and do not see the pulse signal. Is the engine jitter related to it? Replace the exhaust camshaft position sensor and find that there is still no signal. According to the circuit diagram, the 29 and 36 legs of the engine control unit are interchanged with the pins 30 and 49. The result of the test is that the signal of the intake camshaft position sensor vanishes, which confirms that the engine control unit is normal, and the problem is on the sensor. The camshaft sensor is just changed. Where is the problem? So the line began to be checked. Check the connector of the position sensor of the exhaust camshaft. Because of the aging, the internal pins are deformed, so that each insert can not be inserted in place. After the connector is repaired, the signal of the exhaust camshaft position sensor is measured, and it is normal. After debugging the trouble code, it is found that although the fault light is no longer light, the engine is still shaking. Again, no fault code was found. It is also normal to check the idle speed of the idle speed. So far, the real cause of engine jitter has not been found. Considering the high mileage of the vehicle, it is suspected that its internal carbon deposit is excessive. Looking at the endoscope, it is found that the coke is more serious. The intake manifold is ready to be removed for clearance. When removed, it was found that the crankcase ventilation duct was blocked and the trachea was deflated. Troubleshooting: replace crankcase ventilation valve, troubleshooting trial run.