cannot fill tank with gas very fast, nozzle shuts off

What is your question?

When filling the gas tank, the gas pump nozzle shuts off. Have to put gas in very slowly.The purge valve and 2 O2 sensors have been replaced. Get codes PO420 and PO456. Could this be the canister, the fuel tank vent valves or something else.Can the vent valves be replaced if that is the problem or does a new gas tank w the 2 vent valves have to be replaced?

What makes this problem better or worse?

nothing affects the condition

How long has your 2007 Jeep Patriot had this problem?

2 months