I think I remember reading on here (in the archives thru a search) of a gentleman who spent a week or 2 going thru every part of the system only to find a partly broken wire under the sill plate under the drivers door. He had tested the valve, did a smoke test on the fuel tank and gas cap/filler hose, along with checking and replacing vacuum hoses, driving the car with a VOM attached so he could see the ECU sending a signal to the purge valve, even replacing the purge valve (after testing it), and a host of other diagnostics (he was glad he wasn't paying a shop to do it all). Then he found that broken wire, fixed it and the problem went away.
If you're in a state that requires emission testing, you might want to pull the #13 fuse (passenger side) to clear the codes, and not drive more than 10 miles before the test so it doesn't come on. Fortunately my state doesn't test, and I just let the light glow at me (it's been coming on for almost the 3 years I've had the car, for that same problem). I clear it every so often (to check for other codes), and after 3 starts and shut offs or about 12 miles it'll come back on for that code. It doesn't effect the running of the car, but it's just a PIA that the light is on. The common fix is to replace the valve and solenoid. On my own car I replaced a section of steel line that had rusted out in multiple places, but I'm betting I missed some more along with some rubber/plastic tubing too. I bought the valve years ago, but the screws holding it on are all sorts of rusty, and might need more than just the valve replaced by this time.