Hello, I just bought my first jeep. I am in love with it and the great community that goes with it. All the jeep waves and even had a duck left on the door already. It's a 2013 Sahara Unlimited. When I bought it the tire light was on. The car lot agreed to fix it but they are 3 months out on labor. I've been trying to figure it out on my own but stumped. It has aftermarket 17 inch wheels with 35's.
-The dash is showing the correct psi on each tire and is set per the door sticker 35 psi.
- I have tried setting air pressure to 38, 40.
-The spare has a TPMS installed that is transmitting (just had that installed) thought that was the problem.
- I've cleared the codes and after driving they come back on.

 

You can go to any tire dealer and they have a tool to check the sensors and make sure they are working.

 

I would say that the tire change got rid of the Mopar sensors perhaps. They are a specific frequency depending on model years of Jeep. IE my 2008 won't work with yours. Try and get your nippers on JScan app and the wifi/Bluetooth dongle and check what is happening. You will need the JScan anyway. That U code should be corrected as it relates to the CANBUS. Try clearing the codes to see if the U code goes away.