I'm up in absurdly cold VT right now, where the temp is -1. When I went to my 2008 A4 this evening, the tire inflation sensor told me that my tires were underinflated. I went to the gas station and inflated the tires (they were, indeed, down to about 20 psi).

Questions: should I listen to the sensor in weather this cold; when I get somewhere it's warmer should I let some air out of the tires; and is it normal for the OEM tires on an A4 to lose pressure in 0 deg. F temps?

FiveG

 

Yes - it's typical for tire pressure to decrease the colder it gets. Not sure of the threshold on the Audi TPM, but my Crossfire TPMs alert if the tires are underinflated or if any one tire is +/- 2psi of the other tires.

Fill them to the correct pressure when it's in the 20s. Check them if it gets below zero or above 40-50 and air up or down.

Welcome to the north.

 

its simple physics. with warmer temperature the more the air molecules expand. with colder temperatures the air molecules condense, thus resulting in the need to check your tires with weather changes.. every tires lists its cold tire inflation amount on the tire.