Check gas cap?

[Adamcr68]

Started my truck this morning, heard that dreaded ding, expecting check engine light but was relieved it was the evic screen saying check gas cap. I tightened it, white plastic piece inside seemed loose but the seal looked fine. Should I replace with factory or ok to use aftermarket? Are they vented or is their any particular thing I need to get? Calling dealership near me for a price & availibilty, how long can I wait, I don’t want to cause more problems. Thank you

 

[Michael]

Unless there is any visible damage I wouldn’t worry about it fir now. If you keep having issues with it telling you to check it then replace it. This could be just a one off thing for now.

 

[tron67j]

I had similar problem years ago, first ignored it, then used aftermarket to replace and a month later light back on. Used OEM to replace 2nd time, no more problems.

 

[Adamcr68]

I had similar problem years ago, first ignored it, then used aftermarket to replace and a month later light back on. Used OEM to replace 2nd time, no more problems.

Thank you. My local dealer had in stock-30$ going to get it. My wife wanted to know why couldn’t get one from Walmart, I told her our trucks are picky, thanks again

 

[Adamcr68]

Unless there is any visible damage I wouldn’t worry about it fir now. If you keep having issues with it telling you to check it then replace it. This could be just a one off thing for now.

Thank you, I appreciate your response, as far as oem parts go this is not too bad. 30$ for new

 

[srv1]

I picked up a MOPAR cap at rock auto about a month ago for 18 bucks.The dealer is a stealer!

 

[Tach_tech]

The check gas cap light should almost be a sticky. “Check gas cap” doesn’t actually mean there’s anything wrong with it. What it means is that there is an evap leak equivalent to a gas cap missing. It may be the gas cap but could also be anything else in the entire evap system.

They shouldn’t even have that message come up. I deal with customers somewhat regularly that come in saying they replaced the gas cap but the lights still on. Only to find out there’s actually something else wrong.

 

[Adamcr68]

The check gas cap light should almost be a sticky. “Check gas cap” doesn’t actually mean there’s anything wrong with it. What it means is that there is an evap leak equivalent to a gas cap missing. It may be the gas cap but could also be anything else in the entire evap system.

They shouldn’t even have that message come up. I deal with customers somewhat regularly that come in saying they replaced the gas cap but the lights still on. Only to find out there’s actually something else wrong.

Add me to the list, put cap on during lunch started a few times & light still on when I drove home. What is the next thing I should check? Thanks!

 

[Tach_tech]

Add me to the list, put cap on during lunch started a few times & light still on when I drove home. What is the next thing I should check? Thanks!

That’s the other issue with the light. Even if the gas cap was the issue, it could take up to a few weeks for the necessary tests to complete and pass before the light will clear on its own.

So I would clear the codes with a reader, if you don’t have one, do a battery disconnect for 30 minutes, and just wait and see if it comes back.

Otherwise a smoke/pressure test is the best way to find a leak. Obviously not everyone has the equipment to do that so you can just perform a visual inspection of all the components, but unless something is obviously damaged you likely won’t see anything.

 

[Michael]

One thing works great to get rid of that light is a piece of black tape.

 

[GTyankee]

First things to do is disconnect only the Negative Post on your battery for 15 to 30 minutes.
Then just drive around normally for a couple of days to see if the light goes out.
If the light stays on, drive to your Autozone, Oriellys, Advance auto parts & request that they hook up their Scan Tool. After they do that, it's likely that the scan tool will show that the system has a code of p0456

P0456 Evaporative Emissions System - Small leak detected

Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause: A small leak in any of the EVAP hoses or fuel tank hoses A small leak in the purge valve or vent valve The EVAP Canister may be leaking

Possible Solutions First, using a scan tool activate the vent solenoid, sealing the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the number will stay consistent. If is isn't, the pressure sensor will show that as well. If the system slowly leaks, use a smoke machine and watch for smoke exiting the system at any EVAP component. Any where there is smoke exiting the system, that is the faulty component. Do not pressurize the EVAP system with air pressure. Doing so can damage the purge and vent solenoids in the system.

Read more at: https://www.obd-codes.com/p0456
Copyright OBD-Codes.com

 

[Adamcr68]

First things to do is disconnect only the Negative Post on your battery for 15 to 30 minutes.
Then just drive around normally for a couple of days to see if the light goes out.
If the light stays on, drive to your Autozone, Oriellys, Advance auto parts & request that they hook up their Scan Tool. After they do that, it's likely that the scan tool will show that the system has a code of p0456

P0456 Evaporative Emissions System - Small leak detected

Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause: A small leak in any of the EVAP hoses or fuel tank hoses A small leak in the purge valve or vent valve The EVAP Canister may be leaking

Possible Solutions First, using a scan tool activate the vent solenoid, sealing the system. Then monitor the fuel tank pressure (FTP) sensor. If the system is sealing properly, the number will stay consistent. If is isn't, the pressure sensor will show that as well. If the system slowly leaks, use a smoke machine and watch for smoke exiting the system at any EVAP component. Any where there is smoke exiting the system, that is the faulty component. Do not pressurize the EVAP system with air pressure. Doing so can damage the purge and vent solenoids in the system.

Read more at: https://www.obd-codes.com/p0456
Copyright OBD-Codes.com

Thank you! I appreciate your advice, I should have known it would be as simple as a new gas cap, will follow the steps you & others have recommended. Love this forum!

 

[Quick_Shifter]

Thank you! I appreciate your advice, I should have known it would be as simple as a new gas cap, will follow the steps you & others have recommended. Love this forum!

Just reading this yes disconnect your battery to clear codes. Then proceeded with further diagnostics. I sent you that video wouldn’t hurt to do a visual inspection of the tank and lines while your waiting to re connect your battery

 

[indept]

One thing works great to get rid of that light is a piece of black tape.

Do you use walmart black tape or should the OP get their tape from the dealer.

 

[Adamcr68]

That’s the other issue with the light. Even if the gas cap was the issue, it could take up to a few weeks for the necessary tests to complete and pass before the light will clear on its own.

So I would clear the codes with a reader, if you don’t have one, do a battery disconnect for 30 minutes, and just wait and see if it comes back.

Otherwise a smoke/pressure test is the best way to find a leak. Obviously not everyone has the equipment to do that so you can just perform a visual inspection of all the components, but unless something is obviously damaged you likely won’t see anything.

Unhooked battery-30 min.- started truck both gas cap & check engine light were off hoping it was just the cap but I’ll know what to do if it comes back on. Thank you Tach_ Tech, Gtyankee & Quick-Shifter! I appreciate the help.

 

[GTyankee]

One last thing, in case it was not mentioned
Ram trucks are picky, they work best if you use a Mopar Gas Cap
Sometimes an after market gas cap will just not work

 

[Tach_tech]

One last thing, in case it was not mentioned
Ram trucks are picky, they work best if you use a Mopar Gas Cap
Sometimes an after market gas cap will just not work

100% I’ve seen a lot of aftermarket gas caps leak.

 

[62Blazer]

In regards to the "check gas cap" or the engine MIL illuminating or going out, different codes have different criteria for activating and going out. Meaning that some codes require a certain number of occurrences before it triggers the light, and then a certain amount of time/key cycles/miles before it will turn off the light even if the issue is no longer being detected. Evaporative emissions codes are like this, and another example is misfire codes. If you take your gas cap off and start your engine and drive it typically does not immediately turn on the light. Keep the gas cap off for a period of time, especially during a key cycle, it will eventually come on. Put the gas cap back on and it will not immediately turn off. For a code for a misfire, if the light came on every time it sensed a single misfire the light would be on constantly. Rather it counts up the number of misfires for each cylinder and will activate the light only if it sees them at a high enough frequency (keep in mind that on a typical V-8 engine running at 2,000 rpm will have 8,000 ignition events per minute, or 133 per second.)

 

[James_in_Utah]

Hi,
Just started experiencing this. Started a couple of weeks ago with P0456 and P0456pd setting off the check engine light. Reset those a couple of times, and now no codes, but the Check Gas Cap light comes on every time. I'll start with a new cap, not expecting that to fix it. This is a 2011 Ram 1500 with 201K miles. The dealer wants about $200 to diagnose the problem. Any other suggestions?

 

[Tach_tech]

You can do a visual inspection of all the evap lines,fittings, and hoses but the best way to diagnose it is with a smoke machine and a hoist. A lot of the components are on top of the fuel tank.