As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, LEFT DUCT PRESSURE STABILIZED AT 11 PSI AT IDLE. GROUNDED-YES. PERFORMED NR 1 ENGINE BLEED AIR SYSTEM HEALTH CHECK, REF B737-900 AMM 36-11-00. FOUND HIGH STAGE VALVE BAD. REMOVED AND REPLACED HIGH STAGE VALVE, REF AMM 36-11-06. OPERATIONS CHECK GOOD AND NO LEAKS NOTED.