As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SFO - LANDING GEAR FAILED TO RETRACT AFTER TAKEOFF. AIRCRAFT RETURNED TO STATION WITHOUT INCIDENT. MAINTENANCE REPLACED LEFT MAIN LANDING GEAR UPLOCK PROXIMITY SENSOR ELECTRICAL CONNECTOR. ACCOMPLISHED LANDING GEAR RETRACTION CHECK ON GROUND. LANDING GEAR OPERATION AND POSITION INDICATIONS NORMAL. AIRCRAFT RETURNED TO SERVICE. (Z)