Hey, sorry I'm not on here much. If you have an earlier than e38 ECM (2005 or earlier I believe) you have to get the Dakota working. I can probably help there too but I'd have to know more...
If you're running an E38 or E67 there are a few things you must do (this is to run your tach without a dakota digital unit):
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This is where I learned to bypass the cluster resistor. I haven't seen it anywhere else, I figured I'd give it a shot since my tach was completely dead without it.
-Run a 10K pull up resistor, basically teed into the e38 signal out and the toyota tach signal in "tee" a 10k from 12v hot when running, to the resistor, to the signal wire. You could do all this on the cluster if you can find a clean 12v when on source. If you were to look at the signal on an oscilloscope it would be the same signal but "pulled up" higher.
-You also need to configure (in hp tuners or EFI Live) the tach signal needs to be set to "crank" and the pulses needs to be "9 high" and "10 low". This is found under "tacho" in efi live, for hp tuners:
V8 tach output for 6 cylinder tachometer - https://forum.hptuners.com/showthread.php?15112-V8-tach-output-for-6-cylinder-tachometer
Hope this helps someone, I got a lot of help from this thread- thanks everyone.