thomasmcc

Every couple of weeks the "check engine" light in my '98 ES300 (193K miles)comes on, and my code reader indicates P0440. I know it is something in the EVAP system. I replaced the original gas cap with a new OEM cap, but no change. I do know that there is no pressure release when I loosen the gas cap during a fill-up. So I suspect that I have a loose vacuum hose or my charcoal canister is bad. My questions are:

Is there a vaccum hose which is more prone to leaking or coming loose? If so, where does it come from and where does it go to?

Any other comments would be greatly appreciated!

Regards,
Tom

19psi

or you could have the evap solenoid failing. the best and really only way to test it is to have the factory scan tool to open and close the evap solenoid while you pressurize the evap system with a nitrogen and smoke mixture while you look for leaks. any one of the vacuum lines could be leaking, the canister could be leaking, the gas tank seals could be leaking, etc.

Nad1370

Check the fuel filler tube lip.
It could be rusted and not sealing the gasket on the gas cap.

thomasmcc

Thanks for the suggestion, but I had already scotch-brighted the fuel filler tube lip prior to buying the new gas cap.

Lexmex

I will give you a list, but usually I have seen the charcoanl cannister being the issue.

Charcoal canister (cracked, damaged)
Fuel tank (not likely)
Hose or tube on route to charcoal canister (often a line that goes over the fuel tank)
vacuum hose (cracked damaged) can happen in the engine bay
fuel cap
vapor pressure sensor

ontoy

thomasmcc,
so what did you ended up replacing to solve the P0440 fail code.

RSpi

Just went round 3 with this code. I replaced the fuel cut off valve on top of the tank on a Lexus IS300.