The PCM controls the intake heater relays from data the Intake temp sensor sends it. It controls the fuel heater relay from data the fuel temp sensor sends it. It translates data sent to it by the engine speed sensor and sends signal to tach.
If you don't have remote voltage regulator it is sent data(battery tempature and line votage) so it can determine what voltage rate the alternator put out.
Battery temp is sent by battery temp sensor located under driver's side battery tray and line voltage is sent by ASD relay (Auto Shutdown). I believe the engine speed sensor turns the ASD relay on.