Where to get RPM signal for Innovate LMA3 Aux Box?

[2QUIK6]

Trying to get this aux box hooked up for the WB O2 recorder and trying to figure out where I need to get the RPM signal from to hook to it.
Anyone hooked up with the Innovate Aux Box LMA-3 done this and which signal to use, is there one going to the ECM or is there one coming off the coil/IM somewhere that I should use?
Thanks

 

[Mike Licht]

There is a white wire with a green connector right behind the alternator, that is the RPM tap
Mike

 

[2QUIK6]

Great, thx Mike. I take it then the '-'ch just goes to chassis ground in this case since there is no "sensor ground" ??

 

[Mike Licht]

the unit is grounded so in most cases you dont even need to add the ground
for RPM
Mike