Volvo: Engine swap

Question
QUESTION: I have an opportunity to buy a 2003 v70 non turbo in excellent condition, but the engine was replaced a short time ago, but the ecm was NOT, diagnostics tell me this: "ECM having problems communicating with other modules" with my vida dice set up,and I can't erase all the codes, car dashboard tells me, "It's ready for service", I can get another ECM (Denso) with same part numbers as original, can I download the software from Volvo Tech, to make the vehicle run properly? Volvo tech says all DTC's must be removed before software download.
I really need this car, and it's right in my price range right now, with software downloads, another ecm etc, included.
Thanks for your Knowledge, Time and PATIENCE.
P.S. (Please post, because I can't seem to get a decent answer from any of the forums.)

ANSWER: It is not true that all codes must be removed before software can be installed but all modules must be online.If you have any modules that are offline you have to find out which ones and fix them .Some of the vehicles can have there ecm wiped but you have to have the vehicle that it came out of to do so ,otherwise it cannot be done and a replacement ecu must be bought .The old ecm should be ok to use with the replacement engine providing all the parts were changed over from the old engine .Hope this helps rob ...

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QUESTION: The guys that did the swap were sued by the state of Ct. and the previous owner, the st. also pulled their ticket, and fined them 20,000. I can only gather that they swapped motors but not all the modules, a hodgepodge of modules, I can't clear all the DTC's  Your answer is very good though, it gives me the option. I have a another ecm coming, and when I get the Vida software I can use one of their downloads "P/N 8691XXX. to make the ECM Virgin.
Thanks very much Robert, you are a major help !

Answer
I would have to check but i think that the module has to be in the origanal vehicle ,not sure if you put it in your vehicle that you could wipe it ,but it is worth a try .Sorry to here about your problems with your garage .It happens ,hope you get it sorted .