As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, NOSE DOOR OPEN, WARNING MSG. RETURNED TO AIRPORT, MSG PERSISTED THROUGH APPROACH & LANDING. MSG CAME ON & OFF 4 TIMES. ADJUSTED PROX SENSOR PX31 IAW AMM 320105. REMOVED ICE BUILDUP IN DOOR RECESS & GVI OF DOOR & SENSOR. PERFORMED OPERATIONS TEST OF PX31 IAW AMM 326100. OPERATIONS CHECKED GOOD.