Gas cap light and CEL

Gas cap light and CEL - FIXED

For the last couple months I have been getting the gas cap loose light and also throwing numerous codes related to the loose cap or evap leak. I have not done a smoke test, but have inspected all the lines and don't see any visible signs of loose fittings or deterioration. All lines actually look good as new. Gas cap threading and rubber look fine as well. Did the vaseline trick, but that didn't help.

The gas cap light and codes have a routine that seems related to the amount of gas in the tank. Starting with no codes or gas light present, I'll fill up the tank. After a couple key cycles or on or around 1/8th of a tank used, the gas light comes on. A couple more key cycles or on or around 3/4th a tank engine light comes on. On or around 1/4th tank left the gas light goes off. On or 1/8th tank left the CEL clears and engine light goes off. Once they clear my scanner will also not pickup any codes.

This has been routine for the last 10 fill ups or so. The codes are 0451, 0456 and 0457. It has thrown a couple other evap related codes as well that I cant remember, but they are in the P045* sequence related to evap leak. Each time, the codes could be different, maybe just on or two, or a combination of all of them.

Has anyone experienced this and did you find a culprit?


FIXED: I removed the tether, see post 13.

I keep getting a "small leak in the evap system" code, dealer said it was a bad sensor and replaced it for my 100$ ded, but it continues to come on. I keep clearing it but am getting fed up so im going back to the ram dealership soon to figure it out. This may or may not help you, but I thought I'd share

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MarshRam said:

For the last couple months I have been getting the gas cap loose light and also throwing numerous codes related to the loose cap or evap leak. I have not done a smoke test, but have inspected all the lines and don't see any visible signs of loose fittings or deterioration. All lines actually look good as new. Gas cap threading and rubber look fine as well. Did the vaseline trick, but that didn't help.

The gas cap light and codes have a routine that seems related to the amount of gas in the tank. Starting with no codes or gas light present, I'll fill up the tank. After a couple key cycles or on or around 1/8th of a tank used, the gas light comes on. A couple more key cycles or on or around 3/4th a tank engine light comes on. On or around 1/4th tank left the gas light goes off. On or 1/8th tank left the CEL clears and engine light goes off. Once they clear my scanner will also not pickup any codes.

This has been routine for the last 10 fill ups or so. The codes are 0451, 0456 and 0457. It has thrown a couple other evap related codes as well that I cant remember, but they are in the P045* sequence related to evap leak. Each time, the codes could be different, maybe just on or two, or a combination of all of them.

Has anyone experienced this and did you find a culprit?

Click to expand...

Replace the gas cap.

slightly_low_ram said:

I keep getting a "small leak in the evap system" code, dealer said it was a bad sensor and replaced it for my 100$ ded, but it continues to come on. I keep clearing it but am getting fed up so im going back to the ram dealership soon to figure it out. This may or may not help you, but I thought I'd share

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Click to expand...

Thanks. Let me know what happens with round2 at the dealership. I'm hoping the symptoms I'm having can determine the issue.. I had the evap cels and gas cap light in my 07, but it was not like the routine relationship to the amount of gas in the tank as I explained, they just stayed on and nothing ever reset. I filled up around half tank the last couple rounds and didn't have anything reset as it does once I let it get to quarter tank or so. Odd that it comes and goes based on the amount of gas in the tank. There has to be an explanation.

Dangulo said:

Replace the gas cap.

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I put one on today, we'll see what happens. But, the gas cap I have has no noticeable wear/damage in the threads nor rubber.

I had that on my old f150. A squirrel had chewed a hole in the vent line on top of the gas tank. Couldn't see it where it was located had to wrap my arms around gas tank and just feel the lines. It was the line that runs from top of tank back to top of filler neck that allows you're tank to vent while fueling. The system that trips the cell doesn't operate constantly, it just periodically checks vacuum I believe, it might be pressure. Anyway I replaced that 1' length of rubber hose and problem was fixed.

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Ramnewbie said:

I had that on my old f150. A squirrel had chewed a hole in the vent line on top of the gas tank. Couldn't see it where it was located had to wrap my arms around gas tank and just feel the lines. It was the line that runs from top of tank back to top of filler neck that allows you're tank to vent while fueling. The system that trips the cell doesn't operate constantly, it just periodically checks vacuum I believe, it might be pressure. Anyway I replaced that 1' length of rubber hose and problem was fixed.

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Thanks! Those lines above the tank and up to the neck are hard to get to and I had to feel portions of them rather than get a close look.. I'll do another check in that area. What you said makes a lot of sense if it is indeed the purpose of that line. Much appreciated.

A smoke test or air pressure test is really the only way to know for sure if there is a leak. It doesn’t take a lot to make a leak, even if everything “looks” ok. It may not even have a leak, could be a faulty ESIM,wiring,PCM etc.

Evap leaks can be very tricky to diagnose, since the parameters to run the tests are very stringent, as well take a long time to complete. That’s why you could clear the code and it may take weeks or months for it to come back.

Also there is no P0451 dtc for your truck? Did you mean P0441? That’s a evap purge system performance which opens up even more possible faulty components.

Tach_tech said:

A smoke test or air pressure test is really the only way to know for sure if there is a leak. It doesn’t take a lot to make a leak, even if everything “looks” ok. It may not even have a leak, could be a faulty ESIM,wiring,PCM etc.

Evap leaks can be very tricky to diagnose, since the parameters to run the tests are very stringent, as well take a long time to complete. That’s why you could clear the code and it may take weeks or months for it to come back.

Also there is no P0451 dtc for your truck? Did you mean P0441? That’s a evap purge system performance which opens up even more possible faulty components.

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You are completely correct however I absolutely hate taking my truck somewhere to get it worked on. Very few actual mechanics left anymore, just a whole lot if parts changers. If there is any possibility that I can fix it myself I will.

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You absolutely can fix it yourself but without a scan tool and some special equipment you’re just going to be throwing parts at it and guessing.

Tach_tech said:

You absolutely can fix it yourself but without a scan tool and some special equipment you’re just going to be throwing parts at it and guessing.

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I just don't start changing parts, I'll inspect everything I can see and make sure that there is nothing obviously wrong. If it's mechanical and I can see it I can fix it. When it comes to chasing rouge electrons I'm totally lost, that's the reason I get the extended warranty on my vehicles. Pretty much if it's electrical I don't even mess with it.

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Tach_tech said:

A smoke test or air pressure test is really the only way to know for sure if there is a leak. It doesn’t take a lot to make a leak, even if everything “looks” ok. It may not even have a leak, could be a faulty ESIM,wiring,PCM etc.

Evap leaks can be very tricky to diagnose, since the parameters to run the tests are very stringent, as well take a long time to complete. That’s why you could clear the code and it may take weeks or months for it to come back.

Also there is no P0451 dtc for your truck? Did you mean P0441? That’s a evap purge system performance which opens up even more possible faulty components.

Click to expand...

Yes it was 0441, my mistake. That one only came up one time and it came up with three other codes. Another time it only threw one code. And another time it had 3 codes. Right now it is only throwing 2 codes. I'm getting below half a tank right now, so over the next couple days as I reach 1/4 tank the codes will clear on their own and everything will be fine again until I fill up the tank and start the process all over.

I do not want to throw parts at it, but it will likely cost me a couple hundred bucks minimum for smoke and pressure test. Other than the lines, I could replace a few likely culprits for under that price. Idk, tough call. I have no good mechanics where I am at, nothing but a new horror story every single time I have taken a vehicle in. If I didn't need my truck, I would have another honda in the driveway. Lol..

So it appears I have fixed my issue after almost 3 months and nearly 15 fill ups.. One thing I notice when I put my gas cap on is the tether will cause the cap to slightly recoil. Not major by any means and I thought it has always done this, even before the issue started. Maybe my recollection is incorrect. Anyhow, I initially thought it was a stupid idea, but I had nothing to lose so I removed the tether and two gas fill ups since, no more gas cap light or CELs. Wow...

MarshRam said:

So it appears I have fixed my issue after almost 3 months and nearly 15 fill ups.. One thing I notice when I put my gas cap on is the tether will cause the cap to slightly recoil. Not major by any means and I thought it has always done this, even before the issue started. Maybe my recollection is incorrect. Anyhow, I initially thought it was a stupid idea, but I had nothing to lose so I removed the tether and two gas fill ups since, no more gas cap light or CELs. Wow...

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Sometimes the simplest of things can cause the most frustration. Hope that fixes you're problem.

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Are you still trouble free with the gas cap light and check engine light? My 2017 with just over 400 miles started showing the gas cap light a couple of days ago and now today the check engine light also came on. I don't have a code reader so I'm not sure what codes it's bringing up. It'll be sometime next week before I can take it to the dealer.

Anybody ever have these lights come on with so few miles on the truck? I'm hoping that it's not a sign of things to come as I've only had the truck for a couple of weeks.

Well, you have a new Ram. You very likely did not tighten the gas cap good enough. Make sure it clicks a few times. After a key cycle or two or even while driving after the first start the gas cap light should go away. If that doesn't work then see the dealer.

This started happening to me in the 80k range. I have reason to believe the end of the tether that plugs into the cap has tightened, maybe due to gunk, swelling, stiffness and is causing the cap to slightly recoil??? I haven't tried to diagnose further since I have been trouble fee ever since I unplugging it.

I doubt this is your issue and if my aforementioned recommendation doesn't work, see the dealer.You could have an evap leak. New trucks can come with various issues. Imagine trying to do quality control on every piece of every truck that came off the line, not gonna happen! Little defects on new trucks aren't surprising.

I hope my recommendation works, but if not, let the dealer figure it out. Your entitled to it after all that cash you just dropped... Good luck!

Thanks. I took it off and put it back on after the light first came on. I'll try it again and if it doesn't go away later in the week I'll contact the dealer.

Well I took the cap back off and tightened it until it clicked 3 or 4 times. I have been driving it for the last few days since then and still have the gas cap light and check engine light on. Looks like I'll have to make a trip to the dealer. It's frustrating to have to be taking a truck with less than 500 miles on it back to the dealer already. Hopefully it's a simple fix that will put everything back to normal.

ClarkandAddison said:

Well I took the cap back off and tightened it until it clicked 3 or 4 times. I have been driving it for the last few days since then and still have the gas cap light and check engine light on. Looks like I'll have to make a trip to the dealer. It's frustrating to have to be taking a truck with less than 500 miles on it back to the dealer already. Hopefully it's a simple fix that will put everything back to normal.

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Yep, definitely see the dealer, sounds like it is something other than lack of tightening the cap enough.

Well, reviving this one unfortunately... After 6 months/7k miles of having no issues, I pulled my Superchips and installed a Diablo. First turn of the ignition and the gas light came on and after a few key cycles the cel is back.

Coincidence? I'll report back once I figure out the culprit.