Message center reads Battery High Voltage and Check engine

Don , I had full service on Gen at coach care last week and I had them plug it in and check for any faults they said there were none . When I started to leave the check engine light came on , I had them come out and look at it they had me turn it off and wait 5 minutes to restart to reset computer. Check engine light did not come on . The next day is when the check engine and battery high voltage issued started . I'll call them Monday . Thanks