Chevrolet Camaro 1967-2002 - 98 Z28-resetting computer

OK, do you still disconnect the battery to do this? If so, for how long? wife has a p0442 code on her car. It came on a couple of days after filling up and she has filled up once since. Visually checking, I can't seem to local a problem. She has replaced her gas cap a couple of years ago. Car still runs good for one with 190,000 miles on it.

Battery disconnect has never really done much for me.
When I want to clear codes I turn key one, remove batt and ecm fuse, turn key off, put the fuses back in and restart is and it might need a little goading to relearn idle.
That code the first 2 simple things is too make sure the cap and clicked a few times and the other is to look for hose vacuum leaks specially with that many miles.
Could be a few other things, but those are the cheapest and easiest to do.

Pulled fuses, light went off, havn't done anything to it yet, just trying to see if it is a glitch. Told wife to expect it to come back on. I checked for cracked vacuum lines and found none. Gas cap is on tight, was replaced a couple of years ago, might be bad again. How do you check the purge valve to see if it's bad?