I have a po440 code. Already replaced gas cap. Was told vent valve? Where is it

Hello, The P0440 code indicates a very large leak of the evaporative emission system has been detected. The gas cap being left off is often a cause of this, but other failures can cause this as well. A diagnostic procedure is available in the shop manual for this concern, and should be followed to troubleshoot and find the source of the issue. An evaporative emissions system failure will often not cause any engine performance problems that you would notice. It is affecting the system that prevents fuel emissions from escaping into the atmosphere. The canister vent valve, for what it's worth, is located near the evap canister under the vehicle. I definitely wouldn't recommend throwing parts at this concern until you verify the failure.

SMOKE TEST!