ICM (idle control module) is more properly referred to as ICS- Idle control servo. These are a common problem on Montero's . They do not send a code so there's no clear indication it's bad,,just the symptoms , advice on here and info in the FAQs section.
and sorry , I'm a bad typer and worse editor,,,I meant "is".
Depending on wether or not you have AC , an AT or MT , there are 1 to 3 brass senders on the front of the intake manifold.
Thermostats are cheap- $10- 12 bucks. If you don't know how old the one in there is , buy a new one anyway. I always change mine every 2 years right before my emmision test. Replacing them is regular maintenance type thing anyway.
We all here welcome questions, there are no dumb ones. I and alot of other folks got alot of our "Learning" right here on the Wire.
As you learn the terms and how to navigate this site you will find much info in the FAQs section, enjoy,,untill then keep on asking. <img src="/forums/images/graemlins/cheers.gif" alt="" />.

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.