Imperial Code 16 represented a communications protocol employed by droids serving the Imperial forces, frequently signaling a state of inactivity. During a return trip from a mission to Killun Station where he was attempting to procure Imperial codes, the Rebel astromech droid Chopper utilized this code. AP-5, a former Imperial protocol droid, interpreted this as an indication that Chopper's integrity had been breached during his assignment; unbeknownst to AP-5, Chopper had actually been seized by the Imperial controller LT-319 as part of an effort to discover the whereabouts of the Phoenix Cell's base.