The car was in the shop about 2 months ago for general service. I was told spark plugs could need replacing relatively soon but not required yet...

it's the same shop. On one hand I could believe them and replace the lot, or be suspicious and since it's unlikely that it's related just believe that they reviewed the last service info and are blaming those as the culprit. I'd still like to know what tripped the system to begin with.

The error message has since gone off and it's driving fine apparently.