hi Bill,
You'd have to ask Volvo about their diagnosis. Did they tell you the ECU was bad? I assume they would have tested the system with a replacement ECU by now, but perhaps not. Not sure if anyone on our forum has ever had this issue, but I can tell you that we have not had one fail in the last six years that I have been here (that I am aware of) Hope this helps.
Thanks,
Ralf