Diagnosing EVAP system codes P0442 and P0456 (1 Viewer)

[yngmrostrvile]

Actually the tech blames the fuel cap, not the filler neck.
But I think what you mentioned is worth a try.

If they smoke tested theyd know if the leak was the cap versus fuel filler unless they were smoking through where cap sits.
They might need to go from canister back. Even a smoke test might be hard to find a small leak thats why I suggested soapy solution and comressed air. Great way to find evap leaks and exhaust leaks for cat efficiency codes.

 

[chilllx470]

The last time I tried air pressure from the fuel filler, I could smell gas from around the canister area. This was before replacing the canister.
Will try that again with some soapy water.

 

[yngmrostrvile]

The last time I tried air pressure from the fuel filler, I could smell gas from around the canister area. This was before replacing the canister.
Will try that again with some soapy water.

You want to apply air to the filler neck and block the l8ne to the canister or from the canister back with filler cap on if you know all the line from the canister forward are good. The evap leak has nothing to do with the fuel pressure or return line. The system think fuel vapor is leaking.

 

[chilllx470]

Took it to a shop that has a bunch of equipment to test leaks. He had a machine to check gas caps as well. The cap sealed fine on his machine, but smoke could be seen coming out of it when on the car.
He suggested the fuel filler neck, specifically the threaded part seems to be the culprit.

 

[landarcht]

I brought my 2005 100 to the shop due to CEL P0430 been on for the past many months. A while ago it would stay off after it is turned off, but over the past few months it would come back on the same day after shutting off. The tech told me today it has the pending code of P0456. I had the OEM gas cap replaced about a year ago I think. He said a new OEM canister is about $500. Not sure how or if this can relate to what I originally brought in the car, but he'll be replacing the up and downstream O2 sensors and reset the computer hoping this could keep the CEL off, he thinks the Cat is good. He said when opening the gas cap there's pressure being released which is a good sign, it always has, especially in summer. I also hear a constant buzzing sound like air/pressure leaking or escaping from the gas door when I walk close to the back before filling gas, is that normal? This is before flipping the fuel door open and getting to the gas cap.
Based on this thread, I'll ask him if he checked all the hoses and stuff, but I'm hoping I don't have to replace the Evap canister. I can get about 300 miles out of a tank consistently and don't feel anything out of ordinary while driving. I do smell a bit of gasoline, not a lot, when standing next to rear of the car, is that also normal?

 

[seanz0rz]

I did eventually find my leak, a split in the hose under the rear of the vehicle, at the top, right at the flare of the mating hardline. Replaced everything with new hoses, no problems since.

I do have venting sounds from the cap, especially when I come home from work (work is about 700 feet ASL, home is about 6k feet). I don't really notice it other times.

 

[jbbattag]

I have been chasing these codes for five years on my 03 cruiser. Every shop Swings and misses, as does the dealer. I just live with it

 

[BnvS]

I have the same issue that just started on my 2003 470. Since I don’t have an emissions army where I live is there any way to bypass sensors or fool the ecu somehow so my dashboard doesn’t light up like a Christmas tree every time the self test runs. I could really care less if the evap system is leaking, but I do want to know if another code comes in that will actually affect the performance of the rig like an 02 sensor going bad, etc. it’s annoying I gotta reset it every week and it makes my wife and kid nervous driving with a cel on. I got almost 20 years on this rig I might just do some electrical tape magic and just check the codes every oil change. Anyways, thanks for listening.

Why don't don't you fix it and not deal with trying to bypass the system. They have made it really hard to fool the system. The effort you put into doing that would like have the same cost time and effort

 

[Wah00]

ok, help, Mud-chanics. I replaced gas cap with OEM. Still getting P0442 (#10) EVAP system leak (small leak) and P0430 (#10) Catalyst system efficiency below Threshold Bank 2 code. Techstream hooked up tonight and photo is below.

 

[What is asphalt]

ok, help, Mud-chanics. I replaced gas cap with OEM. Still getting P0442 (#10) EVAP system leak (small leak) and P0430 (#10) Catalyst system efficiency below Threshold Bank 2 code. Techstream hooked up tonight and photo is below.

View attachment 3024750

I had a similar problem which was solved with number 1 of the original post:
Purge valve (or VSV - Vacuum Switching Valve) - This is on the engine (intake) and controls pulling air from the charcoal canister into the engine. This is part number 25860-50100

The purge valve probably stays open which causes more air in the engine than is monitored by the MAF sensor. So the MAF sensor and the catalytic converter do not say the same and give a catalytic converter error. This part is not that expensive and very easy to replace, so maybe worth a try.

 

[Wah00]

I had a similar problem which was solved with number 1 of the original post:
Purge valve (or VSV - Vacuum Switching Valve) - This is on the engine (intake) and controls pulling air from the charcoal canister into the engine. This is part number 25860-50100

The purge valve probably stays open which causes more air in the engine than is monitored by the MAF sensor. So the MAF sensor and the catalytic converter do not say the same and give a catalytic converter error. This part is not that expensive and very easy to replace, so maybe worth a try.

dankeschoen. Will look into this.

 

[fluffyrae]

I’ve just had this code come up right after having the valve cover gaskets replaced. Checked the gas cap and noticed some venting (odd since I’m at sea level), but it otherwise seems fine. Started checking all the hoses in the engine and found the engine air intake hose was folded over on the underside where it meets the intake and there was a gap. Anyone have thoughts as to whether this could have caused the code, or am I dealing with a bad mechanic and an EVAP leak?

 

[What is asphalt]

I’ve just had this code come up right after having the valve cover gaskets replaced. Checked the gas cap and noticed some venting (odd since I’m at sea level), but it otherwise seems fine. Started checking all the hoses in the engine and found the engine air intake hose was folded over on the underside where it meets the intake and there was a gap. Anyone have thoughts as to whether this could have caused the code, or am I dealing with a bad mechanic and an EVAP leak?

Which codes do you exactly have?

 

[fluffyrae]

Which codes do you exactly have?

Just getting P0442

 

[What is asphalt]

Just getting P0442

Than I don't think the air intake hose matters, because the evap system is a closed loop outside the air intake. The lose air intake would more likely trigger a lean fuel mixture code. So my guess is that the p0442 is an entire new problem, but could also be due to a lose or broken vacuum hose which are close to the valve covers and can be damage due to being brittle. This is my insight but also my first car with this system (diesel guy).

 

[WaHoo]

I am chasing a P0456 code as well...I have replaced all the things (minus tubing) that can be replaced...OEM gas cap, OEM vapor canister, OEM canister filter and purge valve...if this doesn't fix it, I am stuck (and will have spare a canister and filter ). Not trying to hijack the thread, but I will share my experiences as we move through this. And yes, I have had 2 shops smoke test the system and that was the consensus...vapor canister and filter. It hurt the wallet a bit, but I need to pass emissions to get the car registered (thanks Northern Virginia).

I also didn't throw any other codes...

 

[What is asphalt]

I am chasing a P0456 code as well...I have replaced all the things (minus tubing) that can be replaced...OEM gas cap, OEM vapor canister, OEM canister filter and purge valve...if this doesn't fix it, I am stuck (and will have spare a canister and filter ). Not trying to hijack the thread, but I will share my experiences as we move through this. And yes, I have had 2 shops smoke test the system and that was the consensus...vapor canister and filter. It hurt the wallet a bit, but I need to pass emissions to get the car registered (thanks Northern Virginia).

I also didn't throw any other codes...

No leakage in the fuel filler neck of the tank or somewhere else in the tank?

 

[WaHoo]

No leakage in the fuel filler neck of the tank or somewhere else in the tank?

I am guessing that is the next step...if the above doesn't fix it I am probably going to have to take it to the dealer...and according to the 2 shops (pretty reputable) it was the canister and filter. Unfortunately I have some trust issues with mechanics in this area...that could have been the "easiest" solution.

 

[What is asphalt]

I am guessing that is the next step...if the above doesn't fix it I am probably going to have to take it to the dealer...and according to the 2 shops (pretty reputable) it was the canister and filter. Unfortunately I have some trust issues with mechanics in this area...that could have been the "easiest" solution.

I recognise the trust issues. Everybody tells you they are a specialist in this car, till you have a problem.

 

[WaHoo]

I recognise the trust issues. Everybody tells you they are a specialist in this car, till you have a problem.

I am sort of fortunate that we have (about an hour away) probably one of the best in the business...the problem is he is an hour away...on a good day.