I have some questions about how the tire pressure monitoring system works. I know that it is based off of a radio frequency for communicating tire pressures. Now, it is my understanding that 'radios' cannot operate when they have no power. Such that, the 'radio' involved in this system, has no power when the engine is off and the powertrain control module also has no power. --Aside that the battery is still connected properly...

That being said, with the vehicle parked, engine off and raised on jacks; if I were to remove one wheel to have a friend fix a tire problem (tire removed and reinstalled with proper pressure) and later in the day reattach the wheel and later drive, would that wheel's tire pressure 'transmitter' still need to be 'reset' with the Learning Tool? If it does, I do not understand how its 'radio' knows whether that wheel is on the vehicle or not. Is it still receiving 'power' with the battery connected? --Then, when I have my battery removed for replacement purposes and say, its unplugged for hours; if the 'radio' receives constant power from the battery and then theres no battery there, wouldn't all four wheels need to be 'relearned' by the tool? --Or, if the vehicles not being used for an extended period, and the negative battery cable is disconnected, that tire pressure radio is also then not receiving power. I've done this before, and not had to get the four transmitters relearned. I don't get it.

 

The tpms sensors have their own integrated batteries. You will not need to have anything done if you take the tires off to have them relearned. They only send pressure while the vehicle is running and changing the position will not effect anything as far as the computer is concerned. You will only need to have it relearned when a sensor is replaced. They have seals that sit on the inside of the rim to keep them from leaking and they generally replace the entire sensor and do the relearn procedure when these seals go bad, or when the battery in the sensor dies. Just have them removed and replace them with valve stems. I got aftermarket tpms which sits on the valve stem and works with either my phone or my android head unit.

 

I see. Well, yesterday, I talked to Ford Service about this and they explained it to me quite understandably. But, thank you for your answer.