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I had the "check fuel cap" alert come across the display, go out in less than one day, then the CEL came on and stayed for 4 days until I took it to the dealership to have it checked out. This happened a couple months ago and they said the code was just that the cap wasn't tight enough. This time they said it was a different code that said there was a possible leak in the VAP system but they were unable to find a leak after 3 tests. The service advisor said that the system is so sensitive that if you have the key turned past position 1 while refueling, it can throw this code b/c it is continually monitoring the car. I don't think I had the key turned on at all. Anyone have this experience? He said if the light comes back on that they will have to do further testing.....

Thanks in advance :)
 

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I had the "check fuel cap" alert come across the display, go out in less than one day, then the CEL came on and stayed for 4 days until I took it to the dealership to have it checked out. This happened a couple months ago and they said the code was just that the cap wasn't tight enough. This time they said it was a different code that said there was a possible leak in the VAP system but they were unable to find a leak after 3 tests. The service advisor said that the system is so sensitive that if you have the key turned past position 1 while refueling, it can throw this code b/c it is continually monitoring the car. I don't think I had the key turned on at all. Anyone have this experience? He said if the light comes back on that they will have to do further testing.....

Thanks in advance :)
The CEL due to not tightening the fuel cap enough will go away after you have tightened the cap and drove for I think it was 3 or 4 drive cycles.

Ask the dealer if they used the HIM/HDS and performed the EVAP test to check the system. They can run a complete test of the system or test components individually. Ask for the test results and report back if they cannot find a solution.

Have you overfilled the gas tank before after the pump turns off? If you overfill, it can lead to a premature failure of the charcoal canister part of the EVAP system over time.

Do you have an aftermarket fuel return kit installed or have you done anything to the fuel system on the car?
 

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The computer isn't continually monitoring the car. The computer waits for a specific set of conditions to be present before running it's tests. This is why the code doesn't show up right away when you leave the station, and doesn't go out right away once you retighten the cap.
 

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I think that you mean that the computer is continuously monitoring the car. If a failure is identified, it registers as a temporary trouble code. If the problem occurs for a predetermined period of time, then the temporary trouble code will be upgraded to a permanent trouble code that would then trigger the DLC to light.
 

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I think that you mean that the computer is continuously monitoring the car. If a failure is identified, it registers as a temporary trouble code. If the problem occurs for a predetermined period of time, then the temporary trouble code will be upgraded to a permanent trouble code that would then trigger the DLC to light.
With most codes you are correct.

I guess what I meant is that it isn't monitoring everything all the time. The EVAP system isn't monitored all the time. The computer runs a test of the EVAP system (draws a vacuum on the fuel tank and watches for leaks) under certain conditions. If the car fails the test it sets a code. When the car is sitting still, not running the computer isn't monitoring the EVAP system.

The computer will set a code depending on how severe the leak is if a leak is detected. On the Civic the first time it detects a leak it tells you to check the fuel cap. If future tests continue to detect a leak it sets a EVAP leak code and turns on the Check Engine Light.

However, if future tests don't detect any leaks it assumes you tightened your cap and turns the light off.
 

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Thanks for the explaination. I know what you mean. I do however believe that my questions to the OP are still valid.
 

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Thanks for the explaination. I know what you mean. I do however believe that my questions to the OP are still valid.
Oh, I agree. I was simply responding to the implication by the dealer that the problem was caused by him having the key on durring fill-up. If that was the case that it would have gone away during the next few drive cycles as you said.

I wasn't disagreeing with any of your statements/questions:redface:. Sorry for the confusion.

I actually agree with what you said. I never top off my tank after the pump stops for exactly the reason you mentioned:thumb:.
 
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