Circulator Pump
 

I just had a circulator pump replaced on my ml320 because during extreme cold weather situations it was squealing really loud.
I went to a local mechanic who specializes in Mercedes repair and he replaced the part with a bosch part. Now I can hear the thing humming when I turn off the engine. Needless to say it's humming when the engine is running also. When the Mercedes part was working correctly you would hear nothing.
Here are the questions.....
First...
Should I go back and have him put in a new Mercedes part, or is the humming bosch part okay?
Secondly....
Can this set off the "Check Engine" light? Because I took it for a ride today and the amber light caught my attention.
Thanks...