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.