As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GUM - FLT 990 - LANDING GEAR FAILED TO RETRACT AFTER TAKEOFF. AIRCRAFT RETURNED TO GUM. MAINTENANCE FOUND SENSOR M-682 GROUND SENSOR SHORTED. REPLACED SENSOR PER MM 32-09-221. SYSTEM CHECKED GOOD AND GEAR RETRACTION CHECKED NORMAL. (X)