check engine light / loose fuel filler cap

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Billy Cormic - 19 Jun 2004 23:58 GMT

Hello,
I went to the mechanic last week because my check engine light was
on. The mechanic ran a test and said the only problem was that I had
a loose fuel filler cap. When I got the car back the check engine
light was off because the mechanic had fixed the problem. However the
next day the check engine light came on again. I am asuming that the
problem is that the fuel filer cap is loose again. What exactlhy is a
loose fuel filler cap and how do I fix it so that the check engine
light goes off?

Thanks,
Billy

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Richard Tomkins - 20 Jun 2004 04:03 GMT

1st.
The Check Engine light is turned on by the Engine Computer to indicate a
failure of some significance in the automobile that must be addressed to
prevent damage or maintain specifications and performance. The Transmission
Computer can also send a signal to the Engine Computer to turn on this
light.

2nd
A mechanic with the proper external diagnostic tool can read the failure
code that may give an indication as to what has failed. The mechanic should
repair the problem and then reset the light.

3rd
A loose Fuel Filler Cap can be a cause that the Engine Computer will turn on
the Check Engine Light, because the fuel system on the car must be
pressurised and a loose cap means the system is not pressurised.

4th
The Fuel Filler Cap is what you unscrew to add Fuel to the car and then
should securely tighten, so that it clicks when you turn it.

5th
If the Fuel Filler Cap is really looses then you had better increase the
amount of force you use to secure it in place and ensure that you are
installing it correctly. Consult your owners manual.

6th
If the Fuel Filler Cap really is secure, then a failure is being logged by
the Engine Computer that must be properly interpreted, take the car to a
Nissan Dealer.

> Hello,
> I went to the mechanic last week because my check engine light was
[quoted text clipped - 8 lines]
> Thanks,
> Billy

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David Efflandt - 20 Jun 2004 16:17 GMT

> 1st.
> The Check Engine light is turned on by the Engine Computer to indicate a
[quoted text clipped - 16 lines]
> The Fuel Filler Cap is what you unscrew to add Fuel to the car and then
> should securely tighten, so that it clicks when you turn it.

3 clicks should be sufficient.

> 5th
> If the Fuel Filler Cap is really looses then you had better increase the
[quoted text clipped - 5 lines]
> the Engine Computer that must be properly interpreted, take the car to a
> Nissan Dealer.

It could be some other problem with the evaporative emission system, like
something cracked or loose hose. I kept getting similar check engine
light code one summer (that dealer thought may have been loose filler
cap), but each time it was cleared it did not return for a couple of
months. Only code I have gotten lately (95 SE) was an obviously
failed injector (1st one was under warranty, this was 3rd time 110k mi).

Signature

David Efflandt - All spam ignored http://www.de-srv.com/

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Filipp Stepanov - 21 Jun 2004 11:56 GMT

Also make sure the engine is off when the car is being fueled.

> 1st.
> The Check Engine light is turned on by the Engine Computer to indicate a
[quoted text clipped - 39 lines]
> > Thanks,
> > Billy

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john smith - 19 Jul 2004 05:48 GMT

The computer monitors the evaporative system and a loose gas cap can set
a check engine light. If the cap is tight you might have a bad cap.
Loosen up the cap to see if pressure releases. If it does your cap is
fine and you should look at the evaporative cannister under the car or
perhaps a loose hose. I had the gas cap loose and the check engine
light came on too. So, be sure to make the cap click three times when
you tighten it after a fill up.

> Hello,
> I went to the mechanic last week because my check engine light was
[quoted text clipped - 8 lines]
> Thanks,
> Billy

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vander@netscape.com - 29 Dec 2004 23:42 GMT

Buy a new gas cap at Autozone - around 7 bucks (you want the non
vented model).

That fixed my check engine light problem.

Also to reset the light, disconnect the negative bat terminal for
about an hour.

>The computer monitors the evaporative system and a loose gas cap can set
>a check engine light. If the cap is tight you might have a bad cap.
[quoted text clipped - 16 lines]
>> Thanks,
>> Billy

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