Clean Air Attempt Gone Awry . . . .

[Maggot]

A check engine light should not be coming on for low windshield wiper fluid-maybe you were being sarcastic. It may illuminate the maintenance light.
Missing or bad gas cap is a big polluter actually. You can get a replacement cap from most auto-part stores.

not sure about that with a smart car but I know people that have bought a cheap cap twice and the only one that would work was an original part from the dealership.