As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - CREW REPORTED AFTER TAKEOFF NOSE GEAR WOULD NOT RETRACT AND CABIN PRESSURIZATION WENT INTO STANDBY. EMERGENCY DECLARED LANDED DFW WITHOUT INCIDENT. REPLACED NOSE LANDING GEAR PISTON THAT WAS BAD. SYSTEM GROUND CHECK NORMAL OPERATION.