Dealer replaced one of the TPC's Car learned the new deal and the TPC ! went away. Turned the key off and the tires showed negative PSI. Reset system again, did it again. How am I getting negative PSI values.
Anyone have any ideas here?

 

I believe you can chose between showing the tire PSI or showing much the system thinks the tire is down. IE 34 PSI in the tire or -2 psi would be what the sytem think you are down by. Doesn't explain the ! though.

 

I have more faith in a $20 tire gauge than in TPC systems.

 

My car is doing the samething, I beleive it is the receiver in the wheel well. My car is still under warranty and I am taking it in to the dealer. I am going to request all sensors and the receiver get replaced.

 

This is correct. It's showing your tire pressure in relation to the target pressure. It will also show +4 if you're 4psi over the correct pressure. Add some air to get your negatives up to zero. It won't give you a red exclamation point warning until you are -7psi or more on any tire.

 

Well on my car, when you turn the car off it tells you -4 on different wheels even when the pressure is good. I will give a update after dealer digs into it. Thank goodness for CPO.

 

I don't think there is a way to calibrate the system. You just have to live knowing your system is right on at -4 psi.