Applying wave and signal theory, I will explain what you are looking at in reference to what the system is set up to do. From the wave forms showing in Stephan’s scope pictorials, #1 & #2, these are readings right at the sensor. Both signal forms are perfect in
accordance with what is required.
What must be looked at is the signal right at its terminus, the ECU. #1 is a classic wave form for a trigger. #2 is a perfect waveform for rpm. By looking at the signal at the terminus, the ECU, one can determine if the signal has been
corrupted or not. Whether it is or is not corrupted is a function of the medium, the coax and the terminus impedance at the ECU. What is required for proper system function is the exact same wave form at the input to the ECU, assuming that the impedance at the ECU is per factory setup
and has not changed or deteriorated. The set up at the ECU input for a given wavefrom/signal is what is important to look at. Assuming that nothing has changed at the ECU, the impedance of the input circuit at the ECU has not changed and is within specification then all that should
happen to the signal is some loss in amplitude but no change in waveform. Then looking at the signal being received at the ECU, one should shake, rattle and roll the transmitting cable from the sensor to the ECU to see if there is proper continuity in the cable. Other than the input
impedance changing which can be assumed has not changed from design requirement then only attenuation of the signal should occur and the fidelity of the waveform should be preserved. Anything other than fidelity of the waveform should be retained other than corruption due to a problem with the
transmitting and the corruption then becomes a function of the transmission coax. A loss in fidelity of the waveform or intermittancy will in fact cause stumbling to complete inoperation of the engine which then can be attributed to the sensor or the cable of transmission. Both sensors
are showing that they are properly operating. The only other cause will be due to some intermittancy in the cable or some extraneous signal pickup from outside of the cable which wil also be due to a problem with the cable. Once again assuming that nothing has changed in the circuitry of
the ECU, if corruption or form deterioration of the waveform is being introduced through the cable of transmission or something external to the cable of transmission then, one can assume the transmission cable has a fault.
If you have any further questions, please ask. And do an
inspection of the waveform(s) at the ECU to get a definite as to whether the waveform at the ECU is proper for correct operation. Don’t forget to somewhat aggressively shake rattle and roll the cable to make sure that cable integrity remains proper for proper ECU response and action at all
times and circumstances.