Tach adapter for 1999-2004 PCM without tach output

[sly]

Shematic:


It's much cheaper to build this if you have the skills than you buy a tach adapter that goes on the power wire to the coils. Use at your own risk. I'm not responsible for you screwing up your car hacking into the wiring.

That said... now a video of this stuff in action via breadboard. Once everything is installed permanently, I'll post pics/vid of that too.

[sly]

Conditioning portion of the circuit isn't needed. In fact, it failed on my car and prevented the tach from getting a signal. Now I have raw signal coming from the diode array. I also seem to have multispark capability so the tach will not read correctly at idle sometimes (jumps up around 2-3x of actual). I've confirmed this with an oscilloscope showing multiple pulses per cylinder. Not sure if that is misfire prevention or what, but it's there.