Had the 07 two weeks. The low tire warning is always on. Tires now all have the proper pressure, but light on anyway. Anyone know why, or an easy fix without going to the dealer?

 

What psi are you running, from playing w/ mine it seems any thing less than 35 sets it off. Try adding 5-10psi more, drive around a little then set them back where you want. Some times the sensor acts up, after airing back up once I went right to 35 & got the warning light, added more air then back to 35 & it was fine.

 

i deflate my 35s down to 20 psi to play on the beach and it goes off at around 25 psi, i run 38 psi for regular driving and when i re-inflate them it takes around 5 mins before the light turns off

 

May just need to reset the sensors. Check your owners manual but it runs along the lines of:
1- With key in ignition turn to on
flip light **** from off to auto a few times until the horn beeps
2- starting at driver side front tire, inflate or deflate tire until horn beeps
3-Repeat for front right tire
4-repeat for back right tire
5-repeat for back left tire
6-start h3 and drive above 20mph for about 5-10 min (doesn't say this line the manual but thats what i have to do)

*note-once the horn beeps you only have about five minutes to reset all the tires otherwise you have to start all over again.

Oh also, you may need to put air in the tires if you choose to use the deflate method.

 

^Like he said, try resetting the sensors. If the spare-tire has a sensor that the truck is trying to utilize, and the sensors haven't been reset, it may be going off of the spare tires sensor.