The chip in my key fob is broken, I don't have another key, can I swap a key and r r
 

EDit:
Oops, can't correct the title it looks like.
What I meant was: can I use the fob and ECM from another similar car?

At the moment my 2007 XC70 is a boat anchor in my driveway.
The little glass-encased chip in the fob got crushed although the key itself and the remote still work. That is the only original key and fob combination that I have.
While at an auto recycler, I found a used fob from a junked 2006 XC70. I was planning on getting that fob programmed, along with the car, as it is my understanding that both need (re)programming.
The cost for this runs into many hundreds of dollars as the car needs to be towed to a Volvo dealer.
I was wondering if I took the ECM from the junked 06 XC70 and swapped it for the one in my car, would the key and ECM "recognize" each other and avoid the cost and trouble of taking the car to the dealer for reprogramming?

No.

Vida, either at the dealership or a private subscription - Can't "reprogram" any module. Once any module (or a remote) is "programmed" to a VIN/car Vida can't change that. A company such as xemodex might be able to. (actually you can program any car to accept any remote, if the correct frequency - you just need the bag the remote came in - to get the pin Number. That's the only place that PIN is written and you can't program a car to accept the remote signal without it. )

The ECM is the engine control module - not the main computer in the car. The chip key "codes" are stored in the CEM. The remote actually talks to the UEM (upper electronic module) - that's the circuit board glued to the back of the inside rear view mirror glass.

If you changed the CEM so that you could use a junkyard key - most other modules won't work - some cars even the DDM/PDM (drivers and passenger door modules) won't work - you won't be able to roll the windows down! (or use the ac, or start the engine - you get the idea)

The cheapest way is to buy (from Volvo) a precut key (they only need your VIN). And have them program the car to accept the signal from the new key. If you have a switchblade style key - you only need the key half. Or you could buy the rubber handled single key (that does not have a remote attached) Cheapest I've heard is about $200 for a single key, cut and programmed.

Others have tried buying uncut keys from ebay. Problem with that is finding someone that can cut that kind of key, then praying the copy is good enough to actually turn the door and ignition locks. Then you have to find a dealer willing to "program" with your aftermarket key. If you order a cut key from Volvo - if it does not turn in the door or ignition - you don't have to pay for it.

Thanks hoonk.
I guess that pretty much clears that up and saves me another trip to the wrecker's yard.
I've found a local (Ottawa, Ontario) locksmith that says he has the equipment to program the car and a new fob so I'll make an appointment for him to come over and see how that turns out. Otherwise, it will have to be a trip, via a tow truck, to the dealer...

I would like to add to what Hoonk said about getting an uncut key done by someone. As someone who has been in that business, cutting those keys suck! They are calling "sidewinder" keys, among other things. And you would need to find a locksmith to cut it, most places do not have the specific machine for them.