As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI TO GATE THE FLIGHT CREW REPORTED SMOKE IN THE AFT CABIN AREA. PASSENGERS WERE DEPLANED AT GATE. THE PROBLEM WAS TRACED BACK TO SPEED SENSOR RELAY ON 20VE PANEL. IT WAS VERIFIED BY THE PITOT STATIC SYSTEM TEST WHICH CAUSED HX FAN TO INTERMITTENTLY SHUT OFF AT AIRSPEEDS OF LESS THAN 120 KNOTS.