P0456 code

[SteelGreyM]

Hi all. I have a p0456 code. Which is Evap system leak detected. I started by replacing the gas cap which did not fix it. Couldn’t find much other info online that is e46 specific. Could someone point me in the right direction?

I’m thinking to smoke test the car.

[lemoose]

Fuel tank breather attached right under your airbox. $150 part and 10 minute job

[oceansize]

Time to do a smoke test. You will likely spend time chasing when a smoke test can (most of the time) give you a clear answer concerning leaks.

Edit: lemoose seems confident so maybe?

[SteelGreyM]

Dmtl valve thing under your airbox. $50 part and 10 minute job

I open my hood to see the bottom hose unplugged. Not sure how that happened… I think that will solve it! You freaking wizard

[cobra]

I open my hood to see the bottom hose unplugged. Not sure how that happened… I think that will solve it! You freaking wizard

It's very weakly plugged in. Nice catch!

[sapote]

With the hose disconnected then why no lean code it’s after the MAF sensor?

[SteelGreyM]

With the hose disconnected then why no lean code it’s after the MAF sensor?

It was disconnected but very loosely attached. I don’t think much air got past. But I’d imagine even a little leak can throw a code… so yeah good question…

[WestBankM4]

I've been chasing this same issue and it's intermittent when P0456 pops on. Usually takes a few hundred miles before it triggers, I reset it and keep throwing parts at the problem.

I've replaced the fuel tank breather valve (purge valve), fuel cap and the DTML pump in the rear. The fuel pump is OEM new as well. There is a rubber hose someone was telling me about that runs from the gas cap location down to the fuel tank and I had purchased the hose from a member selling his own on this very forum, but I've unfortunately misplaced it. If someone remembers the seller of said rear fuel hose, that would be helpful. Other than that, any other rubber hoses I can replace with OEM?

[heinzboehmer]

There is a rubber hose someone was telling me about that runs from the gas cap location down to the fuel tank and I had purchased the hose from a member selling his own on this very forum, but I've unfortunately misplaced it. If someone remembers the seller of said rear fuel hose, that would be helpful.

https://nam3forum.com/forums/forum/classifieds/members-parts-for-sale-wtb/e46/72708-bmw-all-e46-40mm-fuel-filler-hose-includes-m3

[WestBankM4]

Bringing this back to the top because I've finally completed my homemade smoke tester using a pickle jar and bicycle pump.

For P0456, where should I be hooking up the smoke tube on the S54? I plan to remove the MAF and hook the hose up to that rubber intake arm, any other locations? All the videos online are non-S54's.

[WestBankM4]

Sorry to bring this back to the top but it's bugging me this P0456 code. New development is when I fill up my gas tank I smell fuel inside the cabin.

Like I've said, I've replaced,

OEM Fuel Cap
Fuel Tank Breather Valve (Purge Valve)
DTML pump.
OEM Fuel Pump
Rubber hose from neck filler to gas tank

Now that there's a fuel smell inside the cabin, could it be any of the hoses that sit near the fuel pump? I can't find anything and this leak is starting to get on my nerves. Worst case scenario I buy a whole new gas tank but I've read it's rarely the case. Any ideas where I should be looking?

[Albino09]

Bringing this back to the top because I've finally completed my homemade smoke tester using a pickle jar and bicycle pump.

For P0456, where should I be hooking up the smoke tube on the S54? I plan to remove the MAF and hook the hose up to that rubber intake arm, any other locations? All the videos online are non-S54's.

First I would use your smoke tester through the fuel filler neck. P0456 is a diagnostic that's run after a recent fuel fill from a nearly empty tank (maybe 1/4 left). When a fuel tank is nearly empty, the remaining volume of the fuel tank will be full of fuel vapors. As the liquid fuel displaces those vapors, it is pushed into the charcoal canister which, theoretically, should eliminate the smell as it either exits to atmosphere or is recirculated back to the intake to be burned off. To check P0456, the car will close the purge valve to "seal" the system once the car is turned off. As the fuel tank's temperature returns to ambient, the pressure should also change at a relative rate. If the pressure drops too much, a leak is detected and P0456 is stored.

Based on what you've mentioned replacing, have you checked your charcoal canister and the connections to it? Since you mention a strong fuel smell, I am wondering if your leak is between the fuel tank and the canister itself.

[heinzboehmer]

Completely blind guess, but you replaced your fuel pump recently right? Did you also replace the gasket between the pump and tank?

If the old one is torn/deformed, it might be letting vapors leak into the cabin. Smoke tester connected to the fuel filler neck should make this leak pretty obvious.

[WestBankM4]

Completely blind guess, but you replaced your fuel pump recently right? Did you also replace the gasket between the pump and tank?

If the old one is torn/deformed, it might be letting vapors leak into the cabin. Smoke tester connected to the fuel filler neck should make this leak pretty obvious.

When I did the fuel pump, I replaced all the gasket with OEM as well.

Based on what Albino09 and you just told me Heinze, I'll hook it into the filler neck, didn't think about it being from the rear. I hooked my smoke machine to the front of the car but didn't think the rear because I've replaced that charcoal canister and visually inspected the surrounding lines. Let me give this a go and report back, thank you for the help and suggestions boys.

[ugaexploder]

When I did the fuel pump, I replaced all the gasket with OEM as well.

Based on what Albino09 and you just told me Heinze, I'll hook it into the filler neck, didn't think about it being from the rear. I hooked my smoke machine to the front of the car but didn't think the rear because I've replaced that charcoal canister and visually inspected the surrounding lines. Let me give this a go and report back, thank you for the help and suggestions boys.

Curious about any updates on this one...I think I also have an EVAP leak somewhere even though I'm getting an error code 232.