As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GEAR WOULD NOT RETRACT AFTER TAKEOFF. ALL THREE RED AND GREEN LIGHTS. COMPLETED QRH. CHECKED MANUAL GEAR ACCESS DOOR CLOSED CYCLED GEAR WOULD NOT RETRACT. GROUNDED - YES. VERIFIED FAULT. ACCOMPLISHED B737-800 FIM 32-30 TASK 815. SUSPECT ALT EXTENSION SOLENOID VALVE INTERMITTENT. REMOVED AND REPLACED LANDING GEAR CONTROL VALVE PER B737-800 AMM 32-31-51. GEAR CHECK GOOD NO LEAKS.