Y-code: A US Naval Aviation term meaning that it was a piece of equipment that was recieved bad from the repair shop. The part that the O level was trying to replace was defective when it was installed on the plane. If you are the technician that worked on the gear then you will get into trouble for sending out faulty gear. That is if the Y-code was found to be Valid. Y-codes are the technicians nightmare.
Harris: "Dam man I got Y-code last week on that ducer that I fixed."
Cortes: "Well was it a valid Y-code?"
Harris: "Hell no it wasn't. Stupid as O level techs. I was forced to A-799 it back to them with a little note attaced"
Cortes: "What did the note say?"
Harris: "It said Next time try the on/off switch dumb ass"