service light is on

Because your battery isn't dead. H

You need a new one.

Perhaps it needs service.

Could be a reason as simple as a headlamp burned out to a sensor malfunction. Get the codes set in the BCM and look it up.

Probably loose gas cap syndrome. Be sure to tighten cap past a couple of clicks after getting gas. Rick

Your service light is broke and is in need of service.

Any one of a dozen possible reasons. Gas cap not on tight or defective, fuel trouble, ignition trouble, faulty sensor somewhere. You'll probably have to take it to a shop and get the fault code(s) from the computer read. If the light is on a code has been generated and stored.