Thanks for the info. I actually got the info from my Volvo service manager after I wrote the post. The crash sensor unit is indeed expensive, $1,229 (part only) at Volvo. Does not seem to be available anywhere else.

The good news is that it probably is not the unit. I just had keyless remote installed this weekend. While they did a very neat job, they evidently cut into the steering column wiring harness for power, which Volvo tells me is a no-no. They said the sudden voltage draw by the locks probably caused the fault. If this is what caused it, the accessory shop that did the work will pay for it (I already spoke to them). I hope that is all it is, else $1,229 plus installation to fix. I would probably install it myself to save the 2 hours labor it would cost.

Will let you know.