PC-12 Captain reported an autopilot and yaw damper failure during cruise flight; followed the QRH but pulled incorrect circuit breakers resulting in additional equipment failures. The circuit breakers were reset; restoring some systems; but the crew diverted to an alternate airport and landed.

Narrative

Flight Crew experienced an Auto Pilot (AP) Fail Crew Alert System (CAS); followed by a Yaw Damper (YD) Fail CAS at 16000 MSL. First Officer (FO) was pilot flying (PF); while pilot-in-command (PIC) was pilot monitoring (PM). The PIC immediately referred to the aircraft quick resource handbook (QRH) for the first AP Fail CAS and while doing so; the second YD Fail CAS signaled. The PIC referenced the YD Fail CAS as priority and began the QRH step procedures. When coming to the Circuit Breaker (CB) opening; PIC confirmed with FO by finger pointing to what was thought to be the correct CBs. When opening both CBs as directed by the QRH; Display Units (DUs) 3 and 4 went blank and came back online once CB was closed. The Flight Management System (FMS) data was lost for the flight and cascading CAS messages illuminated in flight. Once CBs were closed and DUs came back online; the PIC requested from Air Traffic Control (ATC) a blocked altitude and heading to mitigate the observations further. When a remedy could not be found and given the distance to the planned destination; the flight crew opted to 'land as soon as practical;' thus choosing ZZZ to divert to as to contact maintenance. After landing; flight crew contacted maintenance to advise observations and experience. Though AP and YD CAS messages were observed; and the QRH referenced; it was concluded that the flight crew opened the wrong CBs (the attributing MAU (Modular Avionics Unit) CBs; rather than the A/P SERVO CB and A/P SERVO ENABLE CBs that were directly above the MAU CBs); thus resulting in the DU failures. Maintenance requested the AP failure be written up and deferred given this was the originating factor. A Safety Report is being drafted as the flight crew inadvertently/mistakenly opened the wrong CBs during QRH review and while in flight.