It's just logic. A series of yes/no tests. You know anybody with a OBD-II code reader / scanner? You could check the IAT sensor temp with that. The IAT sensor provides input to the PCM which then based on that and other factors like the MAF sensor controls spark and fuel injector pulses. Theoretically if the PCM is seeing a way too low temp from a bogus IAT sensor then it would push the fuel injectors as if it was a very cold start. But there is also a rationality test worked into the PCM logic. So even if something is way off the system should run at least mediocre. Borrow a code reader / scanner and check it after the engine has sat for a several hours and the coolant has cooled to ambient temp. If the Intake Air Temp and the Engine Coolant Temp are not in the same range then something is wrong.