Everyone,

I'm new here, but bear with me. In most cases I belive that the tire pressure sensors (which are electronic pressure gauges, and attached to the inside of the wheel/rims) are working as designed and not malfunctioning.

It comes down to simple physics and the "ideal" gas law PV=nRT, or rearranged P=nRT/V. Where P is pressure, n=amount of air, R is a constant, T is temperature, V is tire volume.

Basically, the light goes on and off as pressure changes, and pressure increasees as tire temperature increases. And pressure decreases as tire temperature decreases. The temperature change could be due to weather or friction from driving, or both.

The sensors only come on when tire pressure becomes too low (around 23 psi in my 4runner). Now, I live in Alaska, and my car can experience 100 degree temperature changes in a single day (from heated garage to artic cold).

My winter-time solution is this: In a 50 degree F garage, over-inflate tires by 5 psi-- light should be in good shape and stay off unless your tires get really cold (say -20 F or colder). Sometimes the light might come on when you first get in to drive, but after driving will usually go off due to tires being heated by friction. JUST REMEMBER TO LET SOME AIR OUT IN THE SPRING TIME, or your tires will be way-overinflated.

For summer conditions and 60-70 degree F garage temp, put tire at recommended psi.

I know the light can be a real nuisance for picky people like me, but it is there for a reason. If the pressure light comes on while you are driving, you probably are losing air--Unless you've gone from heated garage to much colder conditions.

When I get in my 4runner and it is outside and -35 deg F, I know my tire pressure light will be lit--so I walk around the vehicle and look at the tires before I get in and drive anywhere.

Hope this clears things up for everyone

Yup, I don't worry about it when I see it comes on in the morning. After driving for a mile or two, the tires should warm up and the light should go off. Doesn't explain the spare tire though. If in fact all tires have the module, then the light should always be on because the spare tire never gets a chance to warm up.

Now if it goes off while driving, then there is probably an issue.

Yup, Yup,

Spare is a whole different story without driving friction. But, I just keep mine slightly over-inflated, and if I ever need it then I will let air out to get the correct pressure for driving. Keeping the spare overinflated helps keep the cold from causing a false low pressure indication from the spare.

Carina71

I put 35 lbs in all of mine when the outside temp's were around 45 degrees, that should get me through the winter here in SW Missouri I will have to let some air out in the spring. Good analysis Carina71, looks like the classes came in handy for something. Also I bet you have a lot of time on your hands in the winter in Alaska Stay warm!!!

35-lb's seemed to fix my problem as well from garage to outside temperatures when the temperature was less than @ 30-degrees