Does a NEW ECM have to be "programed" before it will work ? Or should it be a: "plug n go?"

it should be plug and play.

Thanks for the reply,

I found out when "dealer new" It does have to be programed, new part, old part and the vechile at
a Isuzu Dealership...You can send both ecm's away and they say they can do it, but I'm not going to roll the dice with this new and not cheap part, when someone does it I want to be there and drive it home..I was told it would be a "plug n Play" but he was wrong...

Thanks again
MikeK