As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI OUT IN CABIN AND COCKPIT FILLED WITH SMOKE. RETURNED TO GATE. REMOVED AND REPLACED NR 1 ENGINE SYSTEM A CHECK VALVE. CLEANED RESIDUAL FLUID OUT OF LINE FROM NR 1 ENGINE CHECK VALVE FOR SYSTEM A HEAD PRESSURE. REMOVED AND REPLACED WATER SEPARATOR BAGS, RAN ENGINES AT POWER FOR SEVERAL MINUTES WITH PACKS ON AND OFF. OPS CHECK GOOD.