I have a 2005 dodge grand caravan. Check engine light came on. The technician diagnosed it as P0480. He checked that both fans were operating normally, and turned off the check engine light signal. For the next few days the check engine light would turn on for awhile, then turn off on its own. I took it back in, and they replaced the fan relay. The check engine light stayed off for awhile, but has now turned back on again. The technician says he has no idea of what else could be wrong. Any ideas?