Hey Guys,
I have a 2002 Honda S2000 with about 185k miles on it.
I've had the P1456 CEL code come on and off for the last 2 months. CEL has gone off on its own 2 or 3 times for no apparent reason over this time period. But it always comes back on.
I would check the gas cap for tightness every few days and it did seem to be loose.
SO I replaced the gas cap with a brand new gas cap.... CEL still comes back on. Same code P1456.
I replaced the fuel filler neck with a USED filler neck.... I check the gas cap tightness every few days and it seems to always be tight. CEL still comes back on. Same code. P1456.
I replaced the Charcoal canister purge valve solenoid with a brand new part..... CEL still comes back on.
I replaced the charcoal canister with a USED part.... CEL still comes back on.

What else should I check? What is the best way to go about getting this fixed for good? Take it to a shop for a smoke test?

 

Have you tried resetting the ECU by removing the battery cable for a few minutes, then reconnecting? You will need the anti-theft code for your radio (if it's an OEM one).

 

Yes, I actually just replaced my battery a couple days ago. So coincidentally, yes my battery was disconnected for a minute.
CEL went off after that but came back on after about 100 miles.