From what I can see on your wiring diagrams, your coolant sensor (there is only one) goes straight into the PCM (computer). The are two big plugs on your PCM. One for all the input signals. One for all the output signals. Inside the PCM a lot of magic stuff happens, there are many algrithoms and other stuff I don’t understand, but the computer is smart enough to decide what signal to send to your temp indicator on your dash, it also sends signals to turn on and off your cooling fan, a signal to control your emissions to increase or decrease the pulse width on your injectors (how long their open), and probably a dozen or so other things that are dependant on your engine tempature. BTW, you can probably reset your CEL or SES light by disconnecting a battery lead for a minute or two.