service engine soon

A light on the dashboard of most new cars in the last 10 years. If it lights up while driving, Don't Panic! You can drive at least home or to a mechanic.

A variety of faults could trigger this light. It could be as benign as a disconnected mass airflow sensor. Or it could be an early sign that your transmission needs real attention ASAP. Probably the best saying in this case is that YMMV.

The nice thing about it is that it: A. Makes you aware of an error, as opposed to a oil gauge jerking up and down. B It's easier to comprehend. Windows ignores this easy principle, but showing the details like "Invalid page fault" when an app crashes.

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.