Tachometer needle intermittent not working properly?

Hi Joe, thanks for the fast response, appreciate it. First of all (sorry I forgot to mention this) this is an aftermarket tachometer. I can't check for RPM drop because the wire that carries the signal from ICM (pin 12, tan/yellow wire) to PCM and eventually to tachometer, is dead, 0 volts or pulses. I'm hoping I'm not having a short in that circuit and fried that part of the brand new ICM which could be a possibility, couldn't it?
Again, thanks for your fast response and help.

Hi, nothing to the best of my knowledge.I followed procedures; disconnected the battery, unplug ICM, clean the area thoroughly, and I mean thoroughly. Applied some dielectric grease to ICM, put it back on plugged it in and reconnected battery.
Again, thanks for your fast response and help.

Yes, the new ICM is from Std. Motor Products. Yes, she's running, little rough idle, though. Actually, I ran the koer test again and I got a 332(EGR low flow)and a 411(cant control rpm)codes. Funny thing, I took some voltage reading with the voltmeter from the tachometer service connector and got between 10 and 12 V, but no pulses showed on test light, though.
Thanks again.

I figured as much. This is a new ICM, so there must be a short somewhere in that specific circuit. The one that carries the signal from pin 12 on ICM to #4 on PCM.I guess it's "find that freaking short"time.
Thanks a lot, buddy, appreciate the inputs.

Hey, buddy, welcome to the "ran out of options"club. One more thing to do, get me a bottle of Tylenol's, (for the headaches I am sure l'll have trying to "nip this thing in the bud") before replacing the ICM again. Maybe the manufacturer can help me out.
Thanks for your concern, I'll keep you posted.