Something has thrown a check engine light (CEL).
Best bet would be to take it to a Subaru garage that can read/scan/clear the code, take it to a dealership who can read/scan/clear the code and repair/fix what is causing the code.
Cruise control should also be disabled when a CEL is thrown.
If you can't get to a dealership or garage, I'm sure there are a few people with a data scanner that would be willing to help you find the problem.
Have a look at the
workshops thread if you want to find some one close to home.