As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
YEG- ON TAXI (APU POWER ON), THE CIRCUIT BREAKER FOR THE DCU 2 POPPED. SMOKE FROM THE H13 CIRCUIT BREAKER (EICAS). CIRCUIT BREAKER DID NOT POP. RECEIVED MULTIPLE FAULT STATUS MESSAGES FOR THE DCU 2 AND DCU AURAL 2 FAILURE. EVACUATED AIRCRAFT. MAINTENANCE REPLACED THE DCU NR 2 AND THE CIRCUIT BREAKERS. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.