As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PREFLIGHT, RT PACK LIGHT ILLUMINATED. GROUNDED - YES. REMOVED AND REPLACED AIR CYCLE MACHINE REF. B737-900 AMM 21-51-04-700-802-002 UP TO STEP 3.H.(7)(N). REQUIRED MEL 21-1G REVERSAL PRIOR TO AIR CYCLE MACHINE INSTALLATION TEST. REVERSE MEL 21-1G OPS CK GOOD CLEAR MEL 21-1G, SEAMC DARWIN NOTIFIED.