I have a set of winter wheels, and put new tires on them this season. Both last year and this year, I get an 'inactive' warning every week or two once the weather gets below freezing. It usually resets once the temp goes up, or I reset the system. When I swapped the tires on in November, there were no issues until the temp got into the 20's.

My thought is either a sensor/tire has some moisture in it, or a sensor is on its way out.

Is there any way to find out which sensor(s) are giving the system a problem?

Thanks,
Mike

 

LOL! Sorry, I really did just laugh out loud. Since this seems like a serious question I will give you a serious answer. Pressure is directly related to temperature as long as the volume is constant. Since the volume inside the tire never changes, colder temperature=less pressure. So you don't need to worry, it's normal.

 

Not true, a tire looses about 1 psi a month due to air leakage. Plus every drop of 10F will make your tire pressure go down 1 psi, and increase if it gets warmer. If the weather gets colder, you need to add air to your tire. If it is getting warmer, you will need to take some out.

When measuring tire pressure, always measure cold tires, never when you've driven on them at basically anything over a mile or so, because the tires will heat up and the pressure will increase. This is calculated in when designing the tire, so nothing to worry about.

 

Tire pressure is still at 38 psi when I get the issue. It is not a 'low pressure' warning (I have seen this), it is an 'Inactive' warning.

Mike

 

The scientific law isn't true... interesting. Nice going, saying the same thing I did after saying that it wasn't true.

In that case, I wouldn't know.

 

I am wondering if the batteries are weak, and the cold makes the sensors stop working,,then they warm up a bit, and work?
Did the sensors get "serviced"when the snows were installed...really just an overpriced battery replacement....sometimes a valve core too.

 

+1 Zippy

my local tire store says the battery life is 5-7 years

the OP has a 2008 model ... so he is in the timeframe of end of life of the batteries

when i got my second set of wheels for winters, i ordered a second set of TPMS senders for them from tirerack

the batteries are potted in with a translucent material so i could see the batteries, they look like the coin shaped mercury batteries

the cold weather may cause weak battery voltage to drop further resulting in the "inactive" warning

scott

 

That makes sense, I never thought that they would have replaceable batteries. I will check it out.

Mike

 

I believe the BMW scan tools should indicate which is going out. My suspicion is a bad sensor. However, general rule of thumb is if the sensors are 4+ years old to just replace them all since there is a good chance the others may not be far behind.