What does the code P0505 on the scanner with the check engine lights on ?

Call the Mitsubishi dealer and ask their service or parts department to tell you what that code means. We answered questions like that all the time as a car dealership. Some of the codes in OBD-II are standard for all cars, and some are manufacturer-specific to account for different engineering. Sounds like a P0505 is a manufacturer specific code that the scanner didn't recognize.