Code P0440

[Rusty62]

My 2003 SLE has been setting code P0440 since I bought it. The previous owner had the gas cap replaced and the filler neck cleaned up but still kept giving him the check gas cap message. I recently replaced the intake gaskets and installed a new upper intake. I had the battery disconnected for a long period of time and as a result the code cleared. Before I started the engine I cycled the key to prime the fuel system and check for leaks. On about the 3rd key cycle the DIC displayed “check gas cap” again. The scan tool showed P0440 again. This makes me think it is likely an electrical issue, as the engine had not been started and it didn’t have a chance to pull a vacuum in the tank and test itself for leaks. If this is the case, is there a method to test the purge solenoid, vent solenoid, or tank pressure sensor? Maybe just apply power to the solenoids manually and see if they click?

[SMok3-11]

That code is for the EVAP system, if code P0443 or P0449 aren't present. You will have to do a full EVAP system check. If one or both are present fix those and see if the P0440 code goes away. If I'm not mistaking.....Good Luck

[CMNTMXR57]

Do a search on P0440 and my name. I've discussed this several times.

[Rusty62]

Well it seems that I have it fixed now. Here are the steps I took: 1) Scrubbed all the rust off the filler neck sealing area, put a light coating of grease on it and then a new cap- code came back. 2) Replaced the purge solenoid/valve (the one on the engine)- code came back. 3) Replaced the vent solenoid- code has not come back since, no more “check gas cap!” I popped apart the old vent solenoid and there was quite a bit of dirt through the foam and into the actual valve that likely prevented it from sealing. I have less than $60 in the parts so I'm sure that's still cheaper than taking it in for a smoke test.