What was found
DURING TAXI, RECEIVED A BOTH ENGINES OFF, SMOKE IN THE COCKPIT AND CABIN. FOLLOWED EPC PROCEDURES FOR CABIN COCKPIT FIRE, SMOKE, FUMES, AND SMOKE SUBSIDED. RAN ENGINES AT IDLE AND HIGH POWER WITH NO ABNORMAL ODORS OR HAZE IN CABIN OR FLIGHT DECK IAW AMM 71-00-01. THE NR 2 PACK WAS MAKING A LOUD NOISE WITH THE NR 2 PACK FAILED MESSAGE. REMOVED AND REPLACED THE NR 2 AIR CYCLE MACHINE IAW AMM 21-51-03. OPS CHECKED GOOD.