The ECM detects abnormalities in a car and transmits them to the driver through messages or warning lights. The warning messages sent by the ECM might range from manageable to very serious cases. Either way, no warning message should be ignored as you might not be a good judge at determining the seriousness of an issue or fault.
Therefore, what does it mean for your car if you see a ‘check fuel cap’ warning? What should you do? Continue reading to find out.
What does it mean when the message pops up?
The ‘check fuel cap’ on a Honda car is a very common message that you might see pop up occasionally. The warning alerts you that there is a pressure leak in the gas tank, usually from a missing or loose fuel cap.
When the gas cap is not tightly in place, an air leak is created, through which fuel vapors escape. The system detects this and displays the warning.
You should not fret if you see this message pop up because gas caps are not designed to last forever. During your Honda service, sometimes the technician will check the state of the fuel cap, especially the gasket. A replacement might be needed as the car is subject to age deterioration.
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What are the main causes?
Although the most common cause for the ‘check fuel cap’ warning is a loosely fitted gas cap, other reasons contribute to the warning message.
Missing gas cap
If the gas cap of your tank is missing, you will notice this message immediately. This might happen when you fill up your tank, place the gas cap somewhere else, and close the fuel flap. In this scenario, you might have to replace the gas cap to stop the message from popping up.
Unscrewed gas cap
The fuel cap of your car has to be tightened appropriately to stay put; thus, if the threading of the cap is wearing, the warning might appear. When you screw your gas cap, you’ll hear a final click, which shows that the cap has been properly tightened.
If you do not hear the click anymore, you might check if the cap is still in good condition or consider a replacement.
Faulty gas cap
A faulty gas cap will trigger the warning message. A rubber lining around the fuel cap known as the gasket might wear out over time. If the gasket is bad, the cap won’t fit properly, thereby leading to the escape of gas vapors that will trigger the warning.
Failing purge valve
A canister purge valve is an important part of the EVAP system, which works effectively to reduce emissions. The purge valve works in conjunction with the charcoal canister to channel the fuel vapors to the engine to burn them up.
Once the purge valve fails, you might start to notice some symptoms such as the ‘check fuel cap’ message, the check engine light, increased emissions, reduced engine performance, rough idle, and difficulty in starting the car.
If a faulty purge valve is confirmed, a replacement might be necessary. Otherwise, conduct a further inspection of the EVAP system.
How do you fix it?
If the cause of the warning message is a loose gas cap, you can quickly fix this by tightening the cap. The message might take a couple of hours before clearing.
However, if it does not clear after a while, check the state of the gas cap. Inspect the fuel cap for worn threading and try turning the cap and wait for the final click.
If the cap is worn, you might have to replace it, but if the cause of the issue is a bad gasket, you might consult your mechanic to check if you can get a replacement for that without having to change the cap itself.
If your Honda gas cap requires replacement, it might cost anywhere from $60 to $100. The price might be affected by your location or the model of the car. A fuel cap replacement is one of the easiest parts to replace on a vehicle.
All you have to do is remove the old one and screw the new one on, and you are good to go.
If the gas cap seems fine after inspection, the cause of the message pop-up might be an EVAP leak. Consult a mechanic at once for further inspection if this occurs. It is best not to drive with the car in the meantime if an EVAP leak is suspected.
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What is an EVAP leak?
An EVAP leak indicates an issue in the Evaporative Emission Control System. The fuel tank is a part of the system; thus, a problem with the system might sometimes trigger the ‘check fuel cap’ message. An EVAP leak is a serious issue and should not be treated lightly.
Driving with an EVAP leak could cause fire accidents and put your life and others at risk.
Therefore, if you see the ‘check fuel cap’ message, check if other warning lights are illuminated, especially the check engine light, as an EVAP leak also triggers it. You could try to scan the system using an OBD II scanner to affirm the suspected leak. Either way, professional assistance should be sought as soon as possible.
How to test for an EVAP leak?
Testing for an EVAP leak is not as easy, as you will need special tools. There are multiple methods of testing for an EVAP leak, but I will mention the two most effective ones:
Smoke test
Before rushing to AutoZone or Amazon to buy a smoke machine, you should know that they start from about $700. So for a one-time use, it is not worth it from a DIY perspective.
They are also really hard to find as renting equipment. While on Youtube are various videos of people improvising all sorts of smoke tests, I recommend having the car checked by a professional with access to all the right tools.
Vacuum test
A vacuum test can be done manually using a vacuum pump or by using an engine vacuum gauge. Essentially, you will be connecting the vacuum gauge to the manifold vacuum while the engine is shut.
Now, start the engine and monitor the gauge. It should read around 21 inches of vacuum and remain steady while the car is idling.
Any sporadic drops will indicate that the purge valve is stuck open.
It is not difficult to perform a vacuum test, and the tools needed are not expensive. However, it can be somewhat confusing if you are unfamiliar with most components your car has under the hood.
Check out the video below on testing for EVAP leaks on a Honda Accord. The video will show you step by step what you need to do.
Is it safe to drive with the check fuel cap warning on?
Yes, it is safe to drive with the check fuel cap warning. Pulling over to check the gas cap might seem logical if you see the message pop-up, but it is less safe. Checking the state of the gas cap on a busy road might place the driver at a higher risk. Hence, before inspecting the gas cap, ensure that you park in a safe place.
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Here’s how to reset the check fuel cap message on Honda
Some of you might wonder how to reset the warning light and make the message go away.
The warning message won’t go away unless the problem is fixed. So the best thing to do when you notice the warning show up on the dashboard is to switch off the engine and go and check the fuel cap.
Sometimes just taking the fuel cap off and replacing it will fix the issue.
The warning might still be there for a couple of minutes, so I recommend driving the car around for 10-20 minutes and seeing what’s happening.
If the problem persists, it might indicate that there’s more to it than a poorly tightened fuel cap.
Would a loose fuel cap cause my car not to start or the engine to die?
Although you might be confused by the Engine Light warning coming on, a loose or missing fuel cap should not cause any starting problems with the car or the engine to die. The only issue caused by a faulty fuel cap will be increased emissions, gas smell through the air vents, and the check fuel cap warning on the dashboard.
If you experience any other mechanic problems with the car, you should get it checked by a mechanic as there’s more to it than a damaged or loose fuel cap.
In summary
The ‘check fuel cap’ message is an important message that should not be dismissed. However, before addressing the issue, ensure that you are safely parked.
For instance, if you notice this message on a highway, driving to a less busy area before parking is best to check if the gas cap was loosely fitted on. A loose fuel cap might not be the only reason for the trigger message; hence inspecting the EVAP system as well is something you should consider.
Knock on wood that you are dealing with just a bad or loose fuel cap, allowing you to get it fixed with just $60-$70 or less.
Sources
Evaporative Emission Control (EVAP) System
My name is Jeffrey Williams and I have been a car mechanic for over 35 years. I am currently working NYC Auto Repair Shop, in New York City and recently developed a strong passion about blogging. I decided to put together this blog where I will try and answer the most commonly asked questions I get on a daily basis from my customers.
