TPMS sensors - real device or rotation-based?

[quietlyspinach]

Does the Cooper SE have an actual TPMS sensor installed in each tire? If so, why does it need to be calibrated for several minutes before it's capable of giving an actual reading?

I used to own a 2006 MINI Cooper and it had a TPMS system that used the rotation of the wheels to determine if one was lower than the rest; it could not actually tell you the real tire pressure with no movement. And even then it never read actual numbers; it just knew if it was "low" or not.

So I'm puzzled by 2022 Cooper - it seems like it must have a TPMS in order show real numerical readings, but I don't understand why I can't get those readings when I start up the car in the morning without having to press a button and wait for a few minutes after driving it around.

 

[carrrl]

Yes they are in each wheel (just get some winter wheels without and watch it complain.) Supposedly TPMS sensors do this to save battery power, activating only when in motion.

 

[ColdCase]

You are probably not observing what you think you are observing.

All sensors transmit actual pressure. Simpler computers just receive the signals and indicate low pressure with a light. More sophisticated systems display the numbers for each corner, some also include the spare. Your 2006 was a simple computer.

Tire sensors go to sleep many minutes after not sensing rotation. When asleep they transmit data a couple times an hour or so, to conserve battery. When rotating they wake up and transmit data about twice a minute. They also transmit temperature, battery and fault status among some others if the receiver wants to use it.

How the data is used and displayed is up to how the receiving computer software is encoded. BMW chose to put some smarts in the computer, but other manufactures offer more features and better performance, some less. BMW is in the middle somewhere. The computer needs to determine in which wheel the sensor is located so it can display the pressure by wheel location. Simple computers that light a light don't need to do this. Location is usually determined by rotation direction and signal levels. The delay you see is not a calibration, but the time the computer takes to determine or verify the location of the sensors. Some manufactures chose to display the last recorded data and update, others choose to not display anything untill the location is verified.

Sensor location in ancient systems, like those used in some pacific rim vehicles, is programmed manually. In those cases, after you swap between winter and summer wheels, you return to the dealer to have its computer reprogrammed. Keeps the dealer's service shop busy and adds some cash flow.

There is another thread around here with a more complete description with more precise timing.

I think the Mini/BMW system seems initially slow because the designers chose to not display pressure thats not currently verified for the location. Other manufactures choose to display that last known pressure until it gets updated.

There are a few interesting fault pathologies that can develop and lead to confusion. The one that drives tire shop techs batty is when the sensor reports a temperature sensor fault and the computer lights up the warning light. But their portable scanners don't care about temperature sensors, do not read the fault field so it thinks everything is working. It is actually a bad sensor that the scanner doesn't detect.