Tire pressure light will not turn off

First step, check all of the tires and make sure they are all within 1-2 psi of each other. Next take it for a drive over twenty mph to get all the sensors to turn on and see if the light goes out once the system reads the sensors at the correct pressure. That should reset the message and light if the sensor is working.

If that does not work the easiest would be to stop at a tire shop and simply have them activate the sensor in that wheel. It is possible that the battery in the sensor is getting low and nothing you do will make it reset, or the sensor may have failed. The tool they use will talk to the sensor and read the battery life and see if it is reading the proper pressure as well.