emission codes require numerous monitors to reset to prevent emission testing "cheaters" from clearing codes around the corner from the smog test facility. Some take over 100 miles of driving.
I suspect the purge valve as that seems to be the common issue with that code from the MKZ facebook pages. However, that being said...NEVER "top off"....when the pump stops, remove it.
The most difficult part about taking a car in for warranty work with regards to a CEL, dealerships can be weird about it.
1)the light HAS to be on
2) you have to authorize the diagnostic (agree to pay for it) *if* the problem they find is NOT covered by your warranty
3)the problem has to be "active", i.e. "doing it right now", not "a week ago" or they will say "we could'nt find anything wrong at this time, the car is working properly".
I am always annoyed with how they deal with "warranty" claims with regards to CEL's...rather than give you the benefit of the doubt.
I personally always clear codes for customers for free and then document the code in their car's file and explain to them "if the light comes back on, bring it in....I'll re-scan it. If it's the same code, I'll recommend you let is perform the needed diagnostic so we can find the problem and fix it".
Keep us posted ok?