Important rs question

im hooking up a remote start on my 00 pre runner, and i got it all except the tach wire, i work in a shop that does remote starts and radio and what not, but i dont know what a tach wire does on a remote start can someone explain it to me? and where is it located?

 

Best place to pick up your tach wire is behind the dash cluster... It should be a black wire behind it.. Look close.. Try not to go into the engine bay for a tach.

http://www.the12volt.com/installbay/alarmdetail/2140.html

 

well im just using the tachless mode now, but now that it works my alarm goes off and shows hood trigger on remote when i arm the a
larm