I Know there are a lot of threads about this but here is a question, how often are you guys noticing the (!) in cold weather. I have the stock tires and I am adding air every two weeks. What the h3LL is going on. Is anyone experiencing the same thing?

 

The first cold day this year I got the (!) symbol. I added air to all four on the road and the spare. This was about two weeks ago. Haven't had a problem since. How many dings do you hear when the Jeep starts? The number of dings is the number of tires that are low. If you have only one ding, you might have a very slow leak in a tire. Don't forget the spare.

 

Yeah it's one ding, bet it's the spare. I didn't add air to that one thanks.

 

If the 2008 owner's manual is to be believed, a low spare will not trigger the light or chime.

Page 318:

"A low spare tire will not cause the “Tire Pressure Monitoring Telltale Light” to illuminate or the chime to sound."

How the Jeep knows, beats me. I chalk it up to magic.

I originally thought it might have something to do with motion (since you must travel above 15 mph for up to 10 minutes before the system updates -- implying the system only reads sensors in rotating tires and requires four valid signals), But then how does the Jeep discount the spare if it's sitting still on a cold morning? Ergo, magic.

 

Mine dinged the other day as I run 30psi in my tires, they dipped below that when it was real cold (freezing temps) due to colder air being denser.

 

This is exactly what my Jeep did and haven't had a problem since airing up.

 

If this is to be true I guess I may have a slow leak. I filled the tires to 35psi, Im going to check right now.

 

I went out and checked the pressure and all 4 were still at 35psi. The spare was reading 27psi and with one chime... it's got to be that one. I am going to fill it tom. and I'll let everyone know the results. Screw the manual, let JK-Forum give you the answers

 

If you want to eliminate the problem you can get your tires filled with N2. Air pressure is very temperture sensative. Your pressure will drop 1# for every 10 degree drop in temp. So if you fill your tires during the day, while they are hot, and the temp drops say 20 degrees at night there will be a decrease in up to 4 degrees. So if you filled them to 35 in the morning the sensors are reading 31 and will go off as they are set at 32. N2 will solve this problem.

 

Which makes sense (ha!) until you wonder what it is reading when you start the engine on a frosty morning, sitting stationary in the driveway?

The light and a single chime tell you one tire is low. The manual clearly says this one tire is NOT the spare. None of the tires is rotating at this point, so the sensors can't be using movement to differentiate.

Magic.