I have a 1999 Nissian Sentra with 97,000 miles. I get a OBD II code of P0440, which is "Evaporative Emission System" according to the table of diagnostic codes. The code is intermittent. I replaced the PCV valve, but the P0440 code still appears. What other parts should I replace?

Check gas cap, evap. Canister, and evap. Hoses.