As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAKEOFF THE LEFT LANDING GEAR FAILED TO RETRACT. UPON RECYCLING, THE GEAR WOULD NOT EXTEND. RETURNED TO SLC. REMOVED AND REPLACED A SYSTEM DOWNLOCK PROX SENSOR AND B-SYSTEM DOWNLOCK PROX SENSOR AND CANNON PLUG AT P0136 WITH SERVICEABLE UNIT IAW EMB 120 MM 32-61-01, OPS CHECK GOOD.