2002 Sable shows code P1451

I have an 02 Sable with 45,000 and its showing a code P1451. I've replaced the gas cap and the canister vent valve. I have power to the vent valve and I also tested the ground wire for a short but couldn't find any. Anyone have any ideas what the problem might be?

I have 02 sable and seem to have same problem. I will update if (when) I fix it. Me engine light goes on/off randomly

My problem was the PCM but my light was on all the time. Being that yours goes on/off I'd first check the gas cap and the vent valve near the fuel tank. If both are good check the wiring.