I have a service light on, what does it mean

It looks like a horse shoe

TPMS - Tire Pressure Monitoring System, if it looks like this. Could be black, yellow or red, but all mean the same thing. Possible low tire. To re-set, make sure all tires, including spare, are inflated to specs on drivers door, or chassis where drivers door latches. Then watch this: https://www.youtube.com/watch?v=Bns7QniGBpA

that is the tire pressure warning lamp. Make sure all of the tire pressures including the spare are at 30psi. Also be sure all 4 tires on the ground are the same size. With the vehicle running parked on level ground locate the "set" button down by your knees in the driver's seat. Press the button and hold it while watching the low tire lamp. Keep holding the button until that lamp flashes 3 times then stays off. Now the monitor has been "reset".

Good answer schalk. except the donut spare takes 60psi. And does indeed also nave a monitor on it like you say, don't forget it or the light won't re-set