What could cause the CEL P1456 that only happens after the tank is less than half full and goes out after filled?
P1456 with a caveat
thaxman
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That's an evap system leak. It could be anything from a worn gas cap to a cracked filler tube, broken/leaky evap hose, bad purge solenoid valve, bad vent solenoid valve, etc. When the tank is full the PCM will not check the evap system. It has to wait until the fuel level is within certain levels in order to do it's diagnostic test on the evap system. So, while the light may only come on only when it's less than half full that doesn't mean the problem only exists when it's half full.
Thanks for that explanation. :cheers:
Buffalo4
Mine did the same 5 years or so ago. There's a thread on here where I took pictures of the filler tube taken apart. There's a section where the plastic tube connects to the metal end, I sealed it it with something like silicone which stopped it for years. I just had the code come up last week but then got P1457. Trying the gas cap first of course. On my Accord the 1457 was from a leaking solenoid on the canister near the tank.
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If you can find the leak visually it's usually fairly easy to fix. However, it can be such a small leak that you sometimes will not be able to find it easily. If not, you will need to take it to someone with a smoke machine that can easily and quickly find the leak.
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Here's some pretty good info on this code:
P1456 HONDA Evaporative Emissions Control System Leakage Fuel Tank
P1456 HONDA Evaporative Emissions Control System Leakage Fuel Tank
Here's the thread I was talking about. It's 9 pages but has some good info.
http://www.odyclub.com/forums/24-1999-2004-odyssey/33545-check-engine-light-p1456.html
http://www.odyclub.com/forums/24-1999-2004-odyssey/33545-check-engine-light-p1456.html
Looks like I have a heavy reading assignment.
Before I get into all that, here is the P1456 history:
My Honda indy (retired master tech) looked at it when the tank was full b/c of the code and gas smell. This is after buying a new aftermarket cap and being a militant about tightening it. He made me drive it until it was empty then pulled out the tank and found a broken fitting on top of the tank which lead to a replacement used tank. I got a month or more out of this but the smell came back, so I removed the LR wheel, idled the engine and got under there with a soapy spray bottle. Nothing visible. The next full tank, the code went away, but the smell occasionally returned, and of course the code trips when below a half tank. Before I send him on another labor-intensive wild goose chase, I was hoping to do some elimination myself. So we'll see I guess.
Before I get into all that, here is the P1456 history:
My Honda indy (retired master tech) looked at it when the tank was full b/c of the code and gas smell. This is after buying a new aftermarket cap and being a militant about tightening it. He made me drive it until it was empty then pulled out the tank and found a broken fitting on top of the tank which lead to a replacement used tank. I got a month or more out of this but the smell came back, so I removed the LR wheel, idled the engine and got under there with a soapy spray bottle. Nothing visible. The next full tank, the code went away, but the smell occasionally returned, and of course the code trips when below a half tank. Before I send him on another labor-intensive wild goose chase, I was hoping to do some elimination myself. So we'll see I guess.
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Take it to someone with a smoke machine. A smoke machine will find the leak in minutes.
Help with leak! I've been searching the forum for answers but this post seems to verify my thoughts. Background: over the last several months/even a year or so I have received codes for the evap system indicating small leak. Yesterday I filled up my tank, had 400 lbs in the back of the van, and parked on a slight incline. Fuel was coming down the back of the fuel tank. I took out the cargo and parked on a level surface and it stopped. After reading some posts I decided to look at the fuel pump. I did not find and cracks or fuel seepage to indicate this is where the problem is occurring. The dealership said it could be a broken line from rodents, etc. I feel strongly that the fuel leak had something to do with a full tank and a leak from around where the filler neck goes in to the tank? Any thoughts? Are there vent hoses or other places I should consider the leak originating from? Could it still be from the fuel pump? Help much appreciated!
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Yes, there are vent lines that attach on the top of the tank. It could come from any of those or the fuel filler.
After investigating the fuel pump I found the plastic ring extremely loose. I hand tightened as best I could. I believe it was the source of my leak but also the source of my CEL indicating a small evap leak. Real easy to pull carpet back and access area and check if getting a small leak code!
a good indication to split the difference between a malfunctioning solenoid/valve vs. physically damaged lines/fittings is to pay attention when you go to fill up and listen to the 'psssstttt' sound as you open the gas cap. I know on my car I have the P1456 and once in a while I get the 'psssssttttt' when i loosen the gas cap, other times i don't get it. That points to a bad solenoid somewhere rather than an actual leak.
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That is a pretty good theory and check, actually. Might not be 100% but I'd say a good 90-95% anyway. There are only two solenoids in the system, the purge valve and the vent valve. The purge valve is normally closed and should not allow air through. The vent valve is normally open so you have to power it on to close it and then check to see if it leaks.
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