Okay...

As described in this thread, I was able to solve my immediate problem just by taking my car down to AutoZone and have them clear the code for me.

But the code has come back a couple of times. This last time, it came back about an hour after they cleared the code for me, and I'm now embarassed to go back so soon.

I always tighten my gas cap so it clicks properly (as printed on the cap itself), but yesterday when I filled the tank, I noticed that the cap was slightly easier to unscrew than I think it should have been. I think thermal cycling loosens the gas cap a bit on this car. Again, nothing I can do about it other than to tightent it carefully at each fill-up, but that won't make the tank pressure sensor stop "falsing" in the early summer.

I was shown an OBD->Serial connector cable at the owner's meet, and the conclusion was reached that there aren't any electronics needed in the interface, just the proper pinouts and the proper software at the PC's end.

When I do a web search, I only come up with commercial sites that are SELLING the connectors and software. No way I'm spending hundreds just for a connector and some software that should be open-source in the first place.

Does anyone have a link to a site that (a) has the connector pinouts diagrammed, and (b) has freeware and/or open-source software for this?