As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT MAIN GEAR DISAGREE AFTER TAKEOFF. UPON RETURNING TO SLC WE GOT ALL THREE LANDING GEAR DOWN AND LOCKED. (FLT # 4305) CLOSED REMOVED AND REPLACED THE LEFT HAND GEAR UPLOCK PROXIMITY SENSOR S20 (PS11GA), PERFORMED A FUNCTIONAL TEST OF THE LANDING GEAR EXTENSION/RETRACTION SYSTEM IAW AMM GEAR FUNCTIONAL CHECKS ARE GOOD.