I think the fans come on as part of limp in mode in any modern car, and I can see where the computer would have a built in fail safe for cooling system related trouble codes.
My wife drives a 2010 HHR I have yet to see fans running all the time with any of the trouble codes we have encountered so far, however all have been emissions related.
Its my opinion that no engineer would program the fans to run with a code for misfire, TPS 02 sensors etc that would just be too silly for me to comprehend.