As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE YD2 DISCONNECTED WITH ASSOCIATED AP DISCONNECT RE-ENGAGED. YD2 AND AP WOULD NOT ENGAGE ON EITHER SIDE. FO AND FA REPORTED A BURNING SMELL ON FLIGHTDECK. CYCLED A/C POWER YD2 MESSAGE CLEARED. RAN BOTH ENGINES AND CYCLED PACKS AND BLEEDS BUT COULD NOT DUPLICATE SMELL IN COCKPIT.