A couple weeks ago I read about this same problem in my local newspaper (Contra Costa Times), I believe that it was on a GM car. So I do not think this is unique to Volvo. The author of the article described a "drive cycle" to get the OBD system to complete all of its internal tests. Unfortunately I cannot find the article but I do remember it went something like this.

-Accelerate to about 30mph and drive for a few miles. Then coast down to 5mph without using the brakes.
-Accelerate to 55mph and drive a few miles. Then coast down to about 5-10 mph without using the brakes.
-Repeat the above steps a couple of times.

Yes these emmisions systems are expensive and we all get charged a lot to get our smog checks performed. In the end these emmisions control systems have dramatically reduced emmsions from our cars. If the govt did not force us to keep them operating properly, many people would not maintain them. One car that is not operating properly can easily put out the pollution that ten properly functioning cars would put out.

Anyone been to Mexico City lately?