Tires should be set at 35 psi, If its still on you might have to put it in relearn mode and lower the tire psi and raise it back up to proper psi. Sometimes the system will relearn the tire positions on it's own doing this after a drive or immediately when done.
If it's still on you will have to take it to the dealer or say a tire shop like discount tire might have it. The worst case scenario you need a new sensor in a tire or multiples.
To put it in relearn mode here are the steps
1. Turn key to the run position or start the burb.
2. set parking brake
3. turn the light switch till the lights to on by flicking the switch back and forth until the horn honks.
There is a few other tricks to get it to relearn if those don't help.
Hope this helps. It's funny, I have better luck resetting these then the tire guys do at my dealership, and I just do quick service and flushes.