Code P0456 and System Testing

U

Utah_4runner

New member
Hi All,
I have read up on several threads about evap system issues, and have done a lot of research... but still have several questions. Before I get to them let me describe my dilemma.

2005 4runner V8 (2UZ-FE)
I have had issues with codes P0441 (Incorrect Purge Flow), P0455 (Gross Leak), and P0456 (Very Small Leak). I was trying to solve these along with some other issues for quite a wile, so I have done several things that have made it better. More recently I replaced all of the hoses (excluding the metal hard line) with new hoses, replaced the gas cap, and replaced the VSV on the engine, all after testing of course. The hoses looked horrible, and I was getting a small leak from the VSV, although it was still functioning correctly. Along with replacing those parts, I also pulled down the charcoal canister and cleaned it up and did a negative pressure test (vacuum) and it held without any leaks! Now that I have done all of this the only code I am getting is the P0456 (very small leak) code.

So... my questions.
1. I have heard that even though the whole charcoal canister isn't leaking that it can have an internal leak within itself that can throw this code. Can anyone confirm this? Also, can anyone explain other checks I can do with this to verify that it is a good part?
2. I tried testing the whole EVAP system, including the gas tank. I rigged up a vacuum pump and gauge and pulled from the hose going to the VSV on the engine side. I also plugged the hose from the canister to atmosphere. I tried getting a good test, but any time I exceeded 5 inHg I heard something like the evap canister valve open up and off gas on or from the gas gap. Also, if I allowed it to sit at 5 it leaked pretty quickly.. and what I would consider a "gross" leak.

So, what should I do next? Any ideas on how I can solve this?

Thanks!
 
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Finally got it figured out...

Well, I know that nobody replied to my thread... but in case someone else comes across it and needs help here is this for reference.

CHECK ALL OF YOUR HOSES!

I though that I had checked all of my hoses several times, but even though it seemed like it had a good seal it did not. I ended up having a loose hose going from my fuel tank to my charcoal canister which caused the leak. This leak didn't show up until a month or so after replacing my fuel pump, so I think it worked itself loose because it wasn't clipped in as it should be to begin with.

So, after replacing my charcoal canister, VSV valve, gas cap.... I finally dropped the tank again with the suspicion that I had a leak on the fuel sender O ring seal. It ended up being a hose on top of the fuel tank.

Evap leaks suck... good luck tracking them down.

Send me a message if you need any help.
 
great info! i have the p0456 code too. as of this time, i replaced the vsv in the engine. i will find out in the next few days if the code reappear.

Sent from my SM-G930T using Tapatalk
 
I'm having similiar issues. Have a small evap leak, P0456. replaced charcoal canister, the filter that connects to it, and the purge valve or vsv for evap with no luck. code comes back. guess i'll drop the tank next? Would a toyota dealer be able to isolate the actual culprit or would i be wasting more money? i had a local shop diagnose the issue and they told me the evap canister was bad. hum.
 
propilotpete said:
I'm having similiar issues. Have a small evap leak, P0456. replaced charcoal canister, the filter that connects to it, and the purge valve or vsv for evap with no luck. code comes back. guess i'll drop the tank next? Would a toyota dealer be able to isolate the actual culprit or would i be wasting more money? i had a local shop diagnose the issue and they told me the evap canister was bad. hum.
Click to expand...

Have you tried replacing the gas cap?

More people have solved the "small evap leak" replacing the gas cap than any other solution, I would do this before doing anything else, don't cheap out here buy OEM, still not that much money!

If that doesn't solve your issue check all rubber hoses and clamps for wear/leaks.

A dealer will cost you more than you would think and chances are they won't find the issue on the first try, unless you get very lucky, they're no better than any other garage other than they have all the equipment that some other garages might not have, but their knowledge probaly isn't any better than the other garages, a good mechanic is a good mechanic no matter where they work, it's the same with bad mechanics as well and yes dealers do have some bad mechanics. IMHO
 
Last edited:
AuSeeker said:
Have you tried replacing the gas cap?

More people have solved the "small evap leak" replacing the gas cap than any other solution, I would do this before doing anything else, don't cheap out here buy OEM, still not that much money!

If that doesn't solve your issue check all rubber hoses and clamps for wear/leaks.

A dealer will cost you more than you would think and chances are they won't find the issue on the first try, unless you get very lucky, they're no better than any other garage other than they have all the equipment that some other garages might not have, but their knowledge probaly isn't any better than the other garages, a good mechanic is a good mechanic no matter where they work, it's the same with bad mechanics as well and yes dealers do have some bad mechanics. IMHO
Click to expand...

Yes, definitely do a new OEM gas cap as suggested. Another cheap replacement is swapping out the old hoses... sometimes those can get small leaks. Make sure that the O-rings inside of the hoses on the evap canister sealed and didn't roll as you pushed it on. If you haven't messed with the fuel pump, I don't think that the problem would be from that seal. Check the gas filler neck as well, if it looks like it has dry rot you might want to look into that.
 
I've been getting the P0456 code too. FWIW, I am at least one person who replaced the gas cap but did not fix this problem. Now on to the other possible remedies.
 
Dealing with this now, code pops first thing in the am. Replaced gas cap, no change. Will test VSV, and start checking all lines. Really appreciate your post and info.
 
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