EVAP leak

My 1998 Accord LX four cylinder automatic is giving a P1456 EVAP Emission leak detected (fuel tank leak) error. I have cleared the engine light more than once but it comes back after a few days or a week. I have noticed a dip in car mileage.

I found that behind my gas cap, a gasket appears at the top of the filler tube. It appears to have a split. Could that be causing the problem?

Would replacing a part such as 17662-S04-003 possibly resolve the P1456 issue?

To test the theory that the leak is where I suspect it is located, I applied some caulk to try to patch the leak. I will drive it this way for a few weeks to see if the engine light and P1456 come back.

Ken,

Thanks for the help. At least I will not bother with trying to replace the 17662-S04-003.

I have previously taken the car to a dealer and they cleared the code and tightened the gas cap. Before the tank was empty the code came back on. I suppose replacing the gas cap with a new one is fairly inexpensive, so perhaps I should try that next.

I had some difficulty locating the charcoal canister, but did find that it is underneath the car body, below the rear seat on the driver’s side. I believe the canister part number is 17011-S84-A00. I have attached photos corresponding to the diagrams provided.

How would I test the canister for leaks? Do I need some particular type of tool?

How would I test the hoses from the canister to the tank and from the canister to the purge solenoid?

Thanks again,
Gordon

I also found that one of my pictures shows evidence of a leak near the "EVAP bypass solenoid valve". See the first attached image, dark area left of center.

But another picture (second image) taken at a later time seems to not show any evidence of a leak. I am wondering if maybe I had fuel present in the first picture that evaporated by the time I took the second one or it could have been wet dirt from driving in the rain, but why just in that area? This may not help, but does seem odd.

Other comments:

I used my code reader to execute an “EVAP Sys. Leak test”. The code reader indicates “Command Sent” and I heard what sounded like a relay near the canister. This did not cause any malfunction indicator light (Check Engine Light) nor did it set any codes. However, the gas tank is near full so this may not be a legitimate test.

I found some areas that may show evidence of leaks and cleaned them up so that I could check for future evidence of leaking.

The first image is a dirty IAT sensor. The second image is the same sensor cleaned up so that I can check for future leaks.

The third image may indicate leaks from the gas cap. The fourth image is the same area cleaned up so that I can check for future leaks.

I did order a new Honda gas cap online. I will give that a try.

If (after installing the new cap) I get a check engine light, I will provide an update. If I do not get a check engine light after a couple of tanks of gas, I will report presumed success, but that will probably take a few weeks to know.

Since the last time I had the check engine light (and the P1456), I have made two changes. (1) I applied the caulk described in my 6/23/18 post and (2) I replaced the gas cap on 6/30/18. Ken responded to the 6/23/18 post and indicated that the caulk would not help. I have not yet checked the canister for leaks.

I installed a new gas cap on 6/30/2018. The original gas cap had been in use since I bought the car in October 1997. The sticker near the driver’s side door indicates the car was built 09/97.

When the new fuel cap was installed, the car had around a three quarter full gas tank. It has been driven a few times (several trips) so that it is now just over half full. The check engine light has not yet come back on. I think if it gets through the next tank of gas after the current one, the problem is likely fixed by the new gas cap.

No light so far, but I do have a pending code, P1456.

I think the pending P1456 code cleared automatically, which is what I understand the car should do if the test passed the next time it was run. I believe two consecutive measured failures are required to cause a malfunction indicator (check engine) light to be turned on.

I am still on the same tank of gas I was using on 7/2/2018 when I had the pending code, P1456. I have not touched the gas cap since it was replaced on 7/1/2018. The pending code seen on 7/2/2018 may have been set before I had replaced the gas cap (there is no way of knowing at this point). I did not try to clear that pending code (at least not intentionally).

While investigating a problem with my temperature gauge on 7/4/2018, I noticed that my standalone ODB II code reader gave me a green LED. The manual indicates that I would get a yellow LED if I had pending codes.

Today (7/5/2018) I used a Wi-Fi ODB II reader with the ODB Fusion app and on the "diagnostics" screen under the heading "pending" I now have a green check and "No trouble codes are detected." For completeness, under the heading "confirmed" I also have "no trouble codes are detected." This is the test equipment I used when I found the pending code reported on 7/2/2018 (earlier post).

I think this problem is solved, but will continue to monitor through the next tank of gas. The new gas cap seems to have been the solution.

Thank you Ken and 2CarPros. Com.

Unfortunately, the P1456 code and malfunction indicator (check engine) light are back. I suppose I have an actual vacuum leak somewhere, possibly the canister.