As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REF ASA TSR 714008 ON STEP 3, FOUND FAN BYPASS CHECK VALVE WAS MISSING REF B737-800 AMM 21-51-03. ON RH PACK. GROUNDED - YES. REMOVED AND REPLACED PRIMARY HEAT EXCHANGER PLENUM AND DIFFUSER REF B737-800 AMM 21-51-03-400-804, OPS AND LEAK CHECK GOOD.