2000 Mercury Sable - Emissions light

2000 Mercury Sable Engine Emission light stays on

That means you have a problem with the engine controls. What problem depends on the error codes. Have the codes read for free at an auto parts store and post the actual codes - P0123, ect - and we will try and help.

Do you mean the “check engine” light which is often a picture of an engine block?

Or do you mean the light which shows the fuel filler cap?