Model: Lexus ES300 (1994 IMz engine) sedan.
    Symptom: The engine can not start.
    Detection: tested, with high voltage but not fuel (no fuel injection).
    Test the ignition is correct, measuring the crankshaft position sensor, camshaft position sensor, throttle position sensor, water temperature sensor are normal. Switch to the same model of the engine computer and ignition module, the fault remains the same. Check all the sensor and computer connection and computer power supply, grounding are normal. The other parts of the inspection did not find the problem, and then focus on review crankshaft position sensor, found the signal generator rotor (the signal generator rotor installed in the crankshaft timing gear behind), found that the rotor had lost two teeth, and Traces of welding.
    Exclude: Replacement of new pieces after troubleshooting.
    Analysis: signal generator rotor teeth can not be used to repair, after welding metal teeth and other teeth of the metal material is not the same, the magnetic induction is not the same, so the crankshaft position sensor signal sent in the wrong waveform. The engine computer detects the crankshaft position sensor error signal, it is bound to cause the engine to work poorly. Because there was no oscilloscope, can not detect the sensor waveform, and the multimeter can only detect the presence of the signal, the wrong waveform can not judge, so repair the car when the detours.
    Modern high-end car EFI engine or other electronic control system sensor only signal is not enough, the signal waveform must also be correct, otherwise it will cause the electronic control system is not working or not work.