What was found
AVIONIC SMOKE MSG DISPLAYED ON TAXI OUT AT ENG SHUT DOWN. CYCLED AEVC CBS, SMOKE MSG CLEARED, BUT NOW HAVE VENT AVIONICS SYS FAULT, UNABLE TO CLEAR. ALSO, DUE TO SMOKE MSG, WILL NEED TO CYCLE FWC CBS BEFORE DISPATCH. AVIONICS COMPARTMENT SMOKE DETECTOR REPLACED. NO MSGS AT THIS TIME.