When I got my used 2007 Expedition EL, it had 17" after market wheels. So when those tires got low, I bought oem 20" wheel. The new oems have sensors on them, but it's setting off my tps light.

Does any one know how to reset the system?

 

Tire shop can register the sensors to your vehicle. Takes about 10 minutes. Take the vehicle back to shop where you bought the 20 inchers. They should have reset them when they installed the tires