Where did you measure it? At the sensor itself or at the amplifier output?
Unless you have changed the transmission (and hence reluctor wheel tooth count), or the TCU, the amplifier output frequency should be what the TCU is expecting, since the amplifier output frequency equals the sensor signal frequency. The only other way in which the measured frequency could be half what the TCU expects is if the meter you used doesn't respond accurately to non-sinusoidal signals or the circuit is clipping off negative peaks and the meter sees only the positive peaks. Perhaps your TCU needs dual-polarity peaks to recognise the sensor presence?

The amplifier output is how I measured it.

 

Do you get the same frequency measurement if you measure at the amplifier input?

 

Do you get the same frequency measurement if you measure at the amplifier input?

I will check today. Thanks man......

 

First, thank you for all the help. I could not have done this on my own. After test driving and measuring, we are close. I am beginning to think the ECM (cars computer) is more concerned with frequency, as I have achieved the voltage amplification with the recommendations by you guys. I am now wondering if it is a better option to complete eliminate the sensor itself from any part of the circuit, and simply go with a basic sine wave generator (oscillator ?) circuit. This one below caguth my attention. What do you think ? http://www.learningaboutelectronics.com/Articles/Sine-wave-generator-circuit-with-a-transistor.php

 

First, thank you for all the help. I could not have done this on my own. After test driving and measuring, we are close. I am beginning to think the ECM (cars computer) is more concerned with frequency, as I have achieved the voltage amplification with the recommendations by you guys. I am now wondering if it is a better option to complete eliminate the sensor itself from any part of the circuit, and simply go with a basic sine wave generator (oscillator ?) circuit. This one below caguth my attention. What do you think ? http://www.learningaboutelectronics.com/Articles/Sine-wave-generator-circuit-with-a-transistor.php

I find it hard to believe that you would be successful if you use a frequency that is no longer proportional to the shaft speed as reported by the sensor. That is, after all, the purpose of the sensor. If the manufacturer could have saved a few cents by eliminating that sensor, they surely would have.

It would be easy to test your strategy, though. Just use a signal generator app on a smart phone. You can dial in any wave shape and frequency you want, within the audible range at least.

 

I agree with Wayneh, but give the circuit in the link a go if you like. It should give you a ~1kHz sinewave with peaks going above and below the ground rail.

 

I agree with Wayneh, but give the circuit in the link a go if you like. It should give you a ~1kHz sinewave with peaks going above and below the ground rail.

I got several app's last night. I am going to feed various voltage and Hz into the circuit and see what happens. I think this should really find out what we need. Thanks for everything, we are getting close....

 

I find it hard to believe that you would be successful if you use a frequency that is no longer proportional to the shaft speed as reported by the sensor. That is, after all, the purpose of the sensor. If the manufacturer could have saved a few cents by eliminating that sensor, they surely would have.

It would be easy to test your strategy, though. Just use a signal generator app on a smart phone. You can dial in any wave shape and frequency you want, within the audible range at least.

So am I to understand that the audio going out of the signal generator app into the modified headphone jack will send a frequency signal that the computer should recognize ? Wow I really hope it is that simple because with this frequency generator I can dial it in until it literally turns off the lights knowing that the computer is happy with that signal and frequency. Just curious you think it is a square or sine wave? Are all frequencies inherently an audio signal so they can be read by computers ?

 

So am I to understand that the audio going out of the signal generator app into the modified headphone jack will send a frequency signal that the computer should recognize ?

I'm pretty sure you would need to amplify the audio before feeding it to the TCU.

 

I'm pretty sure you would need to amplify the audio before feeding it to the TCU.

Right, I was suggesting plugging it into the circuit that was already in place, using the phone in place of the sensor. As for the wave shape, that will depend on the software and you should be able to choose a range of shapes including sine, square and triangle.