Here's the wire I tapped into when I installed mine on my '92 CX (my '98 EX has the same wire so it's probably for all civic's). I didn't want to pull the gauge cluster and go hacking into the wiring back there so this was the easiest. It's a factory tach lead so you check rpm from the engine bay (for things like setting the idle and whatnot). I just lopped the plug off and attached the green tach wire (I think green, check your paper work) to this wire with a crimp connector.