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      06-17-2013, 04:35 PM   #5
smallseafishie
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Drives: AW 07 e92 335i + AW 11 X5 35d
Join Date: Jun 2007
Location: Atlanta GA

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2007 E92 335i  [0.00]
The batteries aren't always powering the TPMS. They're only "on" when the wheels are rotating (that's why the car requires you to drive for a while when you do a TPMS reset). I'd just replace as they go bad. I'd guess it's a matter of time and mileage. I don't know if the batteries themselves are replaceable as the TPM sensors are potted / epoxied.