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MIL light

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In 2004 Pilot the MIL light (some folks call the engine light) came on. Code reader indicated a P1456 code, which has to do with fuel tank/line vapors. I decided to change out the charcoal canister and bought new one and installed. Drove for 100 miles and MIL light never went off. So, I researched all parts associated with fuel vapors, bought them brand new and installed them. This included total of 5 parts which consists of purge valves and solenoid valves. Drove 100 miles light never went off, which bewildered me. I replaced all parts associated with that code and light still never went off! There's literally nothing else to replace. I had a mechanic turn the light off and after about 10 miles of driving the light came back on. (Mechanic showed the code still read P1456 before he turned light off). Car runs fine, but that stubborn light simply will not go off and I've done all I know to do associated with that code. I can drive with the light on, but I'd rather it be off. Any help from someone smarter than me would be greatly appreciated.
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plplplpl
Gas cap seal? If you can't ensure it's airtight, maybe time for a new, good quality (i.e., not Gates) one? You don't mention changing that, but it has been known to cause that sort of Malfunction Indicator Light light. :)

2004 HONDA PILOT 3.5L V6 Fuel Tank Cap | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.
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charlieboy said:
In 2004 Pilot the MIL light (some folks call the engine light) came on. Code reader indicated a P1456 code, which has to do with fuel tank/line vapors. I decided to change out the charcoal canister and bought new one and installed. Drove for 100 miles and MIL light never went off. So, I researched all parts associated with fuel vapors, bought them brand new and installed them. This included total of 5 parts which consists of purge valves and solenoid valves. Drove 100 miles light never went off, which bewildered me. I replaced all parts associated with that code and light still never went off! There's literally nothing else to replace. I had a mechanic turn the light off and after about 10 miles of driving the light came back on. (Mechanic showed the code still read P1456 before he turned light off). Car runs fine, but that stubborn light simply will not go off and I've done all I know to do associated with that code. I can drive with the light on, but I'd rather it be off. Any help from someone smarter than me would be greatly appreciated.
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Read here: Honda Engine Codes - P1456 | Honda Parts Online. Code is Honda, Nissan, and few other factory specific code, not generic. plplplpl is correct start with gas cap, make sure seal on cap is soft, not cracked, and look at tube to make sure no rust or nicks at the cap sealing surface, check tube for rust, any gas smell? Charcoal canister purge valve usually a P0443, solenoid P0449. If you still have trouble with the leak after inspection of the cap and tube then a hose may have developed a small crack. A smoke machine would be a way to go at that point. Something like this: Romondes SM601 Automotive EVAP Smoke Machine Leak Detector Fuel Pipe Vacuum Diagnostic Tester for All Cars Motorcycles Snowmobiles Light Trucks Boats - Walmart.com that you attach to the green cap under the hood start it and look for leaks.
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plplplpl said:
not Gates
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plplplpl said:
Gas cap seal? If you can't ensure it's airtight, maybe time for a new, good quality (i.e., not Gates) one? You don't mention changing that, but it has been known to cause that sort of Malfunction Indicator Light light. :)

2004 HONDA PILOT 3.5L V6 Fuel Tank Cap | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.
www.rockauto.com
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Thank you but dumb me should have mentioned that the most obvious and easy fix is to first check gas cap. I check it for tight seal constantly and that's not the issue. But thanks for replying and mentioning.
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royalbiggster
Sometimes the gas cap fails internally and can't be seen. Clicking 3 times is a must. As mentioned, when you go to fill up, before you crack open the gas cap, smell around the cap and you should smell no fuel. If you do, this can be due to filler neck seal, or failed gas cap.
Never throw parts at a problem. Quick way to empty your wallet. Always verify first. Just about all parts are verifiable one way or another. If you can't verify than throw money at it. Plus the diagnostic tools are usually good for many other things.
The smoke machine is the first thing I would have done after verifying it wasn't the gas cap. You can make your own for cheap and it is easy. Just follow this video.
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royalbiggster said:
Sometimes the gas cap fails internally and can't be seen. Clicking 3 times is a must. As mentioned, when you go to fill up, before you crack open the gas cap, smell around the cap and you should smell no fuel. If you do, this can be due to filler neck seal, or failed gas cap.
Never throw parts at a problem. Quick way to empty your wallet. Always verify first. Just about all parts are verifiable one way or another. If you can't verify than throw money at it. Plus the diagnostic tools are usually good for many other things.
The smoke machine is the first thing I would have done after verifying it wasn't the gas cap. You can make your own for cheap and it is easy. Just follow this video.
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Funny you mentioned the YouTube.com Mr. Fusion, can be built for $15 with parts from Home Depot.
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WayneM.
The smoke machine will show the way.
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charlieboy said:
Thank you but dumb me should have mentioned that the most obvious and easy fix is to first check gas cap. I check it for tight seal constantly and that's not the issue. But thanks for replying and mentioning.
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In looking at all the things you checked/replaced you didn't mention the Fuel Tank Pressure Sensor next to the charcoal canister. And don't forget the grommet were the filler neck goes into the tank.

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I see you changed the vent and purge valves. The vent valve is normally open and the purge is normally closed. How it works is when the the fuel vapors need to be burned off when the engine is first ran/started, the ECM opens the purge valve and closes the vent valve so vapors are drawn from the canister into the intake that originated in the fuel take, which the ECM monitors vapor pressure inside the tank via the FTPS, when the pressure threshold is met. Remember hoses.
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ckeator
If you are in a northern state, the refineries are in the process of switching from winter to summer blend.

Regardless of where you live, I would reset the light and then add 1-2 cans of SeaFoam to the gas tank and see if it helps. If that doesn’t work, try a new gas cap.
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