Well, that's the 'power unit' of course...!! It says so right on it!
(Sorry I had to!)
But no really... idk what it is but a pic a bit further back so we have some context of where it is mounted might help. Where is it located? Or try & search that 'J121' number on it... or, wipe that white label on the left clean & see if there are part numbers?
That's all I got... I'll be appearing at the Holiday Inn all week... stop on out for some laughs...