When I changed my air pump, I naturally had the battery removed for the 1 hour it took to do the repair. This was enough to reset the check engine light. The pump worked fine after that. That was on 6/22/03 at 68247 miles. I then had the codes checked on 9/3/03 at 70500 miles and none were stored at all. The computer needs to have a certain number of normal drive cycles to reset everything to the noraml state. I guess my time period and miles was enough to do that. I suspect that if had had queried the codes right after the pump was changed, there would have still been a remnant of the faulty air pump notification, i.e., an "unready state". This would have then failed a state emission inspection.