tires with TPMS. Why do they behave like this?

Question

Upon mounting snow wheels (meaning tires + rims + aftermarket TPMS valves) to my 2015 Suzuki Vitara, I have had to drive at above city speed levels for some 10-15 minutes in order for the TPM ECU to pick up in-tire sensor readings. Prior to those 10-15 minutes there was no pressure reading on the vehicle's HUD. (And no, no dealership or whatsoever programming of the new sensors was required. The car just picked them up by itself)

Actually this being a new set of wheels does not make any difference really. Even with the old wheels it was the same deal - i.e. had to drive around for some minutes until a first TPMS reading displayed on the HUD. What I would like to know is why this happens, and more importantly how it happens?

Answer 1

Every TPMS system is different. The one thing they have in common is that per government the sensors must last a minimum of 10 years (it's funny I know).

To accomplish this feat running on batteries the sensors fall asleep when not in use. This usually means driving above 10 to 15 mph before they wake up and transmit a reading. The TPMS sensors contain an accelerometer that wakes them up when they sense the appropriate motion. Also a rapid change in pressure wakes the sensors up. When you first start driving the sensors will usually get awoken as soon as you exceed a particular speed, again every vehicle is different.

When you install new sensors, assuming your car can relearn them by itself (some need to be programmed). The car will take some time to learn the sensors. The car will see that a new set of sensor IDs are following the car and the old ones are not present. This condition triggers a learn event. After some time, to eliminate accidentally learning the sensor of the car next to you, the car will accept the new ID numbers.