I just opened the August issue of Roundel Magazine and the Tech Talk section on pg. 104 has a letter re: TPMS Sleuthing.
According to the article, a 2011 128i with 52,000 miles, had a "system inactive" warning with a tire & exclamation point in the middle come up. It states that average TPM system batteries last 8-10 years. And BMW dealers and most tire shops have a reader to see if the monitor sensor is working.
I have no idea if I changed them last time, and didn't this time either, so I guess I'll just run them until I get an error message.
:
