ok ~ theres 3 sensors on the back of the motor below the intake maifold. 2 of them are like clip like plugs but the other is a green normal plug. i need to know what that sensor is called and what it does. thanks !

 

oil pressure switch
coolant temp switch
oil temp sender

which..?

 

im not sure ~ its the only one thats green ~ i unhooked it and the car still seems to run fine without it. i looked at my freinds car a 91 si hatch with a LS and he never even had it hooked up.