As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PACK LIGHT LH SIDE ILLUMINATED AT GATE. COMPLIED WITH QRH PROCEDURE. LIGHT EXTINGUISHED WITH TRIP RESET. -INFO ONLY-. GROUNDED - YES. L/H PACK/ZONE TEMP CONTROLLER SHOWS NO FAULTS REF B737-900 AMM 21-51-00. FOUND ACM IMPELLER WORN WITH TIP DAMAGE AND SIGNS OF RUBBING ON CASE. REPLACED ACM PER AMM 21-51-04. LK AND OPS CK GOOD. NO OTHER DEFECTS NOTED. ETOPS GROUND VERIFICATION SUCCESSFUL.