I decided to plug one of my tires that had a nail in it today. I removed the wheel, and plugged it. I put the wheel back on and everything was fine, until later in the day my TPS light came on. My pressure is 39 all around, do I have to reset the system or something? anybody have any idea?

 

There shouldn't need to be anything done as far as a reset is concerned.. Did the sensors read 39 or did you use a gauge to measure it? The alarm doesn't normally go off unless the pressure is read at 28 or below.

 

Could the nail or plug have hit the TPMS sensor?

 

where is the TPS mounted? Maybe it was damaged by the weight of the vehicle when the tire went flat.

 

TPS sensor is attached to the valve where you service the tire. Basically on the inside of the rim attached to the outer valve. I think that even if your tire should go flat the sensor should not hit the ground.