What was found
ON APPROACH & LANDING & TAXI IN LEFT DUCT PRESSURE SWUNG BETWEEN 0 AND 65 PSI MULTIPLE TIMES UNTIL ENGINE SHUTDOWN. GROUNDED - YES. REMOVED AND REPLACED L IASC REF MM 21-61-22, ALL TESTS PASSED. ACTIVE IASC MESSAGE CLEARED. THIS CLEARS MEL 21-51-02B, C/N REMOVED,SEAMC DARREN NOTIFIED.