I added coolant and and engine light came on.

Hello, Which type of coolant did you add, where did you pour it into, and did you get the cap secured tightly? If you hear hissing from the cap, if the coolant level is low, if incorrect coolant was mixed with the MB coolant that is in it already, or if you forgot to put the cap on (it happens all the time) you could get an error message. If everything seems fine, that's ok too, just rub down to the auto parts store, and ask them to scan for trouble codes. Make sure to switch the display to the engine temperature display where you normally see your mileage pop up.