The consensus is that the current generation of TPMS should last 7 years or longer so replacing the batteries or the TPMS any sooner would be a waste of time and money. One thing I learned on the forum is that the TPMS will conserve battery power, only actively send data to the vehicle if the TPMS senses a sudden change in pressure or after the vehicle has been driven for ~ 2 miles.
How can it tell how far it's gone?
Number of wheel rotations maybe, else it could be that is how far you typically need to drive before the tires warm enough that the tire pressure increase triggers the TPMS to send data to the vehicle. This explains why in the Volt Owner's Manual it states that to get an accurate reading from the TPMS you need to drive the vehicle for approx. 2 miles.
It just seems easier to have it check for "am I moving?" over intervals and if it gets "yes" like three times in a row, wake up enough to start broadcasting pressure, and fall back asleep again if it gets "no" a number of times in a row as well. Which would make it a time interval of driving, not a distance.
The TPMS also wakes up if you add or remove some air from the tire.
That's why the Volt Owner's Manual states that you need to drive the vehicle for up to 2 miles before the TPMS will provide an updated, more accurate reading.
Concur. What the number on the dash reads is far less important than it not change much unexpectedly or not in line with the rest of the wheels. All four wheels down two PSI overnight? Normal. Only one wheel lost 5 PSI in two days? Problem.
