As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT TO LGA SMOKE EMANATED FROM CENTER CONSOLE. AIRCRAFT DECLARED EMERGENCY, DESCENDED AND MADE UNSCHEDULED LANDING IN STL WITH NO INCIDENT. FOUND PMS MODULE OVERHEATED. DEFERRED PMS SYSTEM IAW MEL 34-37-01. PMS CIRCUIT BREAKER COLLARED. REMOVED AND REPLACED PMS CONTROL UNIT IAW MM 34-63-00, OPERATIONAL CHECK NORMAL.