TPMS Light Only On When Cold (Near Freezing or Below)

So I have really weird issue.... My TPMS light comes on only when the temp gets down around 35-40 degrees or lower!!!!!

It happened last winter when I 1st got it (2015 SR5 CM 5.7) then when the weather broke, no issues all spring, summer, fall and then Bam, as soon as winter hit, it started going off again. Only days when the temp is low.

I live in Middle Tennessee so it's not consistent all winter long as we're not that cold consistently.

When it was in for service last a few weeks ago, I had them check it out. They said they reset the light and it was working fine so it's likely not the batteries. When the batteries go in the sensors, they die quickly, not slowly over a whole winter.

Soooooo.... Anyone have ANY idea what might cause this? I check my pressures at least every other week and keep them inline (including the spare). I'm at a loss....

 

Air pressure changes with ambient temperature. When it gets cold here I put the stock tires to 40psi. Easy for them to drop down to below 35psi when Temps get to the normal sub zero winter we have.

You could check them and then again when temp drops and see how much change your getting

 

This.

 

They will also heat up when you drive, and increase the temp/pressure. So if you're driving to a gas station to check the pressures, they could heat up enough to get back in spec.
If you're checking the tires cold, then it's probably at least one bad sensor. Batteries don't work well when it's cold out.

 

The way I think about it is that when it's cold, all the air molecules want to gather together to keep each other warm, hence the drop in air pressure. When it is hot, they keep their distance so they don't feel each other's heat, hence the higher air pressure.

 

Yep. Simple everyday physics. Described by Boyle, or more accurately, Boyle-Mariotte's law from the 17th century. Ambient temperature goes down, air molecules slow down, tire air pressure goes down. Keep checking your pressures (COLD, i.e. driven less than two miles) and adjusting your pressures; if the outside temperature has changed, your tire pressure has changed. Interesting observation: My nitrogen filled tires seem to have less variation.

 

The TPMS batteries have no issue with -45 - and like the mechanic said, once they die they're dead, they won't come back on without charging.

Nitrogen is less affected by temperature changes than the other elements (mainly oxygen) found in natural air - so 100% nitrogen will have less variation than tires filled with outside air that is only 78% nitrogen