Would this trigger a P0442 code?

[Redog]

I know what the code is, so we don't need to go there.

Gas cap is fine, no broken lines under the hood. Felt the one around the master cylinder and it didn't feel cracked or broken, so I look at the gas cap again.

When I took it off I noticed that the little metal (tin) flap was stuck open. I just gased up and it was closed and no P0442 code was present, two days after I fill up (about 7 miles) the SES comes on and this flap is open.

I'm going to see if I can replace it anyway, need a few small odds and ends for the Alero that I can pick up at the junkyard :awesome:

[sleepyalero]

sounds like that flap would be causing the code.

[zzyzzx]

What is this tin flap that you would be referring to?

Just about any tiny leak in the EFE system can cause a code. That and the gas fumes seem to eat vacuum hoses. On a 2000 Camry that I maintain, I just reset the code and lube the gas cap gasket with oil and it goes away for months.

[a.graham52]

that "flap" will not cause the code. regardless if its open or close, the fuel filler cap is wht ultamitly seals the fuel system.

[xXManwhoreXx]

but that tin flap I think vent the gas when the tank isnt pressurized

[fisdad]

I just had this problem last year. My lights were on for 4 years while I tried to lock this down.

I replaced the purge valve, but that's expensive so do this last.
Buy a new GM gas cap from your dealer. $22 or so, not to bad.

Ultimately, what turned out to be the problem was two things.

1st - My fuel filler neck. The steel line going from the tank to the gas cap, had a tiny rust crack in it that was causing a pressure leak.

2nd - There is a sensor inside the fuel tank on the pump housing assembly. It was the "pressure sending unit" i believe? Anyway, I replaced the entire pump and housing assembly while I was in there. That was the main problem. I found the filler neck in the process. I haven't thrown a code since.

If I remember correctly, the pump and housing from the dealer was only around $300- $350 so again, not a huge deal.

Good luck!