As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX- ON FLIGHT 2147 AFTER ENGINE START WHEN SELECTING BLEEDS ON, HAD VERY LIGHT SMOKE ON FLIGHT DECK. SMOKE CLEARED OUT IN 2 TO 5 MINUTES. REMOVED AND REPLACED NR 1 AND NR 2 ENGINE P2.5/PD AIR SWITCHING VALVE. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.