Check the other tyre pressures !!!and I'm sure you hold in the button to reset it ,when you start the engine ...not 100% sure as its be so long since I had to do that .
You have to hold the "reset" button untill the light blinks or turns on/off ?? not sure which -- then drive for a few minutes to reset the system. Make sure all your tires are up to the right pressure before you reset it though.
On my 04 S - the reset button was under the Emergency brake handle on the front of the console.
turn the ignition off; hold the button and turn the igintion to posn 1, wait till the light blinks and turns yellow, start the car. The light will go out after about 10 seconds.