2004 Volvo XC90 Car is "sputtering"

Intermittant problems like the one you are experiencing and requiring such a long drive is hard to dignose. Sounds like you have a problem in the network but they need to figure out what node is going offline? Could be a relay, maybe the harness, or one of the modules going bad? Are you taking it in to a Volvo dealership or an independent shop? What type of repair have they attempted already?

I have only had it looked at by the Volvo dealership. This is the 4th time it's been in since March - although problems have been occuring since 2006. The DEM has been replaced 2 times (06, 07) - more recently, they have upgraded the communication module - and now are replacing the steering module. I've asked that they check wiring-connections-voltage..anything else I should suggest? They are talking of replacing the DEM again if the steering module does not fix it.

I would need to see all the fault codes but it would seem that you have problem on the low speed communication side of the network? Replacing the DIM (Drivers Information Module) twice I am surprised that they have not gotten there field technical specialist involved? You may have a problem with the Central Electronic Module itself? The harness is usually the last thing you would do if no other problem was found but that would required tearing apart the whole interior of the vehicle. I hope this is still under some warranty? It would be better if they could actually catch the problem happening and start diagnosing at that point? Maybe if some one lives about 50 miles from the shop they could take your vehicle home and hopefully on there drive back in it will act up?