Ran into an interesting issue with my tach

[ca18det_boy]

So awhile back my tach died and I finally got around to getting another cluster so that I'll have a 100% cluster again. Swapped it in and it doesn't want to do anything productive. I've traced the wires from pin 7 on the ECU to my cluster and everything looks good. Tthe FSM states that the tach signal is 1.5V at idle to 3.1V at 2k rpm. I'm getting anywhere from 1.5-6V at the ECU (it likes to jump around on me), 2.2-6.5V at the F51 plug, and 4.5-10V at the cluster. I've checked connections at the CAS and ECU to make sure that they're nice and tight. I then up-wrapped my harness down by the ECU to make sure that I had indeed gotten it correct and just for giggles I checked continuity. Strange thing is that I'm not getting continuity from my F51 plug to my ECU. Tach is reading 900 RPM key in on position and engine off, and the only time it'll move is on decel (it will do the harlem shake). Next step I think will be to try my spare ECU and see if that does anything. I've been using the 94 FSM even though its a 91. So I'm going to download the 91 FSM and see if maybe the tach signal is somewhere else other than pin 7.

[elwesso]

You're definitely going to want to check the 91 FSM, because the wiring on the 94's for a lot of that stuff is considerably different.