Often, when a car reaches a certain age, this light goes on just because. Maybe the wiring is a little fried, or your oil sensor wire is occasionally grounding, or you're out of windshield washer fluid, or your car's brain is feeling poorly.

The auto industry decided that they would put these sensors in new cars so:

  1. They wouldn't have to put all those helpful oil pressure gauges in the dash anymore, and
  2. So that they could award juicy contracts to build the scan tools to 3rd-party parts makers that were kissing their ass.

On some vehicles, you can use a length of wire to close a circuit in your fuse panel, and this light will blink, which you can determine what the hell it is really trying to tell you.