My engine light kept turning on becasue of my gas cap. So I baught a new gas cap reset my engine light and everything was good for about a month and a half then yesturday it said check gas cap and now today the stupid engine light is on again. Any suggestions

 

No one has had this issue?

 

Visit the dealer?

 

Bad sensor?...thats my only guess

 

I know I hate going to the dealer, thought mabey someonelse experienced that happening. I just hope it's not expensive

 

What code is it throwing? P0440 for instance says check the gas cap first, but can be a leak somewhere else in the EVAP system on a Fbody.

 

Yeah that is the code. It will say check gas cap then later the engine light turns on.

 

My light has been on for the past year or so, major evaporative leak. Thought it was the 420.

Changed the gas cap, no. Badd had to replace his filler neck.

I would have figured the light would have burned out by now ... but taxes will fix it.

 

Thats honestly what I'm affraid it might be. It can't be cheap to replace the whole filler neck. Is there anyway to just turn that sensor off with a predator or something like that?

 

Thought Badd's was under warranty. Doesn't look too bad to replace, like 4 screws. The other part may be the canister which was $271, bolted to the gas tank. The rest of the parts are some plumbing.

Think I read that they need to do a smoke test to find the leak. I'll probably pay for that instead of replacing a bunch of parts blindly, as it will be a while before its nice enough here to lay under the car and inspect it.

 

Now my car is having a hard time starting, is that because the engine light is on?

 

For the 12 times they repaired mine the final fix was:
J6441 VALVE,EVAPORATIVE EMISSION CANISTER VENT
P/N 15208329 Valve (net $44.10) Labor ($51.00)

 

Had the gas cap message a few times. Then the check engine light. Went to dealer. It was the vent solenoid, probably the one mentioned above. it sits up in the drivers rear wheel well. They changed it and haven't had a problem since.

Basically, the computer needs to see a certain pressure rise in the gas tank a certain amount of time after the engine is shutdown. If it doesn't see the required rise you get the gas cap message or if it's bad enough, the check engine light.

 

Going to the dealer today crossing my fingers it's nothing expensive

 

EVAP Vent Valve's are extrememly common on these cars. I had two back-to-back Impala's yesterday that both had bad vent valve's. We stock 3-4 of them at all times.

The gas cap message is just an idiot light saying your EVAP system has a large leak. A vent valve that wont close is also a large leak. Its super easy to replace on a lot of these cars too. On an Impala, it only takes a flashlight and a flat blade screwdriver.

 

Good info Matt - I have drawing MW03-111 which is the gas tank to filler door detail - what part do you recommend changing first?

 

Can you post the drawing, I don't have any way to look up drawing #s.

 

i like this guy, good to have a master tech on here
and a journey man like my self,
bow to us bitches!!!!!
iam kidding of course

 

Just had the "check gas cap" message appear last night on my way home. Havent driven it yet today to see if it triggers the check engine light. Not sure if it's because of my downpipe or if it is the EVAP vent code mentioned above. I can get the valve from gmpartsdirect for pretty cheap if it is the valve, just wondering if its easy to replace myself on a GXP or if I should just take it in and pay the labor? Thanks.

 

99% of the time on the cars that are '07 and older, its the EVAP Vent valve. Its really easy to replace. Like I said above all you need is a flat blade screwdriver and a flashlight. You will also need pliers to take off the hose to the valve. If you lay underneath your car behind the LR tire, its mounted by the fuel filler neck inside the LR quarter panel. You have to use the screwdriver to bend a little tab and then the valve slides off the mounting bracket. Remove the hose and connector and transfer over to new valve. Bend the tab back on the bracket and the valve just slides back on making a click noise when its fully seated in the bracket.