As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - ON FLIGHT 2451 LANDING GEAR FAILED TO RETRACT AFTER TAKEOFF. PROX SYSTEM 1 FAULT WAS SHOWN. AIRCRAFT RETURNED TO THE FIELD AND ACCOMPLISHED A UNEVENTFUL LANDING. MAINTENANCE ADJUSTED THE NOSE GEAR PROX SENSOR TARGET PX08. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE. NO PARTS REPLACED.