What was found
LEFT BLEED AIR DUCT PRESSURE INDICATES 9PSI ON THE GROUND WITH ENGINE POWER AT IDLE, A/C PACKS IN AUTO, AND ENGINE ANTI-ICE OFF. RIGHT BLEED AIR DUCT PRESSURE INDICATES NORMAL APROX 20PSI. GROUNDED - YES. PERFORMED INSPECTION OF BLEED AIR SYSTEM OF #1 ENGINE, REF B737-900 AMM 36-00-00. FOUND CONTROL PRESSURE SENSE TUBE ON HIGH PRESSURE VALVE BROKEN. REMOVED AND REPLACED CONTROL PRESSURE SENSE TUBE ON #1 ENGINE HIGH PRESSURE VALVE, REF AMM 36-11-06. NO LEAKS NOTED. PERFORMED DUPLICATE ENGINE RUN @ IDLE, PACKS IN AUTO, ANTI-ICE OFF. RIGHT BLEED AIR DUCT PRESSURE AT 20 PSI, LEFT PRESSURE AT 19PSI. OP CHECK GOOD.