What causes the service light to come on? My car has been sitting in the yard for the last week and I drive it to the gym and the service light comes on. No symptoms noticed. The cavi is an 03 with 115k miles. The only post I found on my search was someone's light on b/c he hit something. Thanks in advance for your useful/helpful replies.

gotta scan the car bro to find out what it is.

The service engine light comes on when the car has detected a problem with the engine or transmission.
Take your car to a local Autozone, or Advance auto parts, or oriley's. They all scan the computer for the codes for free. Then take the car to a repair shop if your not comfortable fixing the car yourself.
The service vehicle light comes on usually when a light bulb is out or something else is wrong that has no bearing on how the vehicle functions.