I have a 2000 Honda Odyssey with a 3.5 liter V-Tec engine. The check engine light came on. I used an OBD2 scanner tool and retreived code P1456, which my service manual shows as "EVAP System Leak Detected (Fuel Tank)." I have since replaced the fuel cap, making sure to twist it 3 or 4 clicks, and then erased the code. The check engine light came on during the next couple of trips, and my scanner later showed the same code. What tests would you recommend next in order to isolate the problem? What is the likely culprit?

When you fill at a station does the nozzle often click off early or prematurely? I suspect a ventilation problem.

Bruce Hunt wrote:

When you fill at a station does the nozzle often click off early or prematurely? I suspect a ventilation problem.

No. The nozzle does not click off early or prematurely when I fill at a station. Any other ideas as to what the problem might be. Thanks

Try these tips:

Fuel filler cap, vacuum connection, fuel tank, fuel tank pressure sensor, evaporative bypass solenoid, evaporative two way valve, evaporative control canister vent shut valve, evaporative control canister and evaporative purge control solenoid. You have to understand that computer codes rarely define the exact component that has failed. All the computer code tells you is that a system that could have one component or many is not operating within the acceptable parameters of the computer's program. Code P1456 means that your vehicle is failing to contain/hold the gas vapors in the gas tank. Retrieving the code in your case was the easy part. If you're lucky it will be simply a replacement gas cap. If it is more than that, you'll need to have the problem diagnosed. Because of the complexity of the system, it may take a couple of hours and some specialized equipment to diagnose the cause. You'll want to be sure the right part is being replaced because some of the components listed are pricey and you don't want to be replacing them on a guess. It would be great if the computer could make a little red flag pop up from the defective component. But then I would have less gray hair and be out a job if that were the case.

It's most likely your gas cap. It's either loose or missing. Our 99 Civic had the same problem. My Passat also had a trouble code for the same thing. When you tighten the cap, you should make it click at least 3 times.

My wife's '01 Odyssey threw a CHECK ENGINE light when I was traveling on business. I asked her to take it to the dealer and $105 later the code was translated to her as a loose gas cap. THe dealer cleared the code. Before I got home from my trip, the light came back no. When I returned home, I used some silicone grease to lube the gasket on the fuel cap. After a few days, the light turned off on its own. I just bought an Actron 9180 OBD2 scanner and found the P1456 in the system. I cleared it using the tool.