Automotive

Loose Gas Cap - Check Engine Light

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  • Mar 7th, 2013 2:33 pm
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Newbie
Aug 25, 2011
33 posts
6 upvotes
London

Loose Gas Cap - Check Engine Light

A few days ago, I left the gas cap loose (didn't click 3 times) and the check engine light came on. At that time I didn't know that it was because of that and drove from London to Toronto (2 hours) thinking I would get my mechanic to check it out, who happens to be in Toronto. When i got to Toronto, I checked and realized that it may be due to the loose gas cap. So I tightened the cap and drove it around normally. The check engine light came off about 1.5 days later. However, the next day it came back on. I was wondering if driving the 2 hours with a loose gas cap could have damaged something? Or will the light turn off permanently after awhile? I haven't put in a new full tank of gas either, thinking that it might be good to just use all the gas and then fill up with new gas for the whole tank instead of half a tank. Can anyone shed some light on my situation?
19 replies
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Apr 4, 2009
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North York
I recently, had a check engine light from a very under inflated front tire (I think). After filling all tires back to spec., the light went off the next day.

It is my understanding the only way to be sure is to have the onboard computer's error/diagnostic code be read, so you know exactly what it is unhappy about.

It is fine to refill the gas tank at any point.
Deal Fanatic
Jan 15, 2006
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Richmond Hill
Car model would help.

If its a early 2000 model corolla this is a common problem due to the evap system if I remember right.
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Apr 17, 2009
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Make and Model would def help.. Easiest way is still to get a OBD reader and find the error code.. I got a cheap BT one that works with my Android phone.. comes in handy..
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[OP]
Newbie
Aug 25, 2011
33 posts
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London
The model is a 2005 Honda Civic Coupe. The gas cap says that if the gas cap is loose, the check engine status light may go on. In the manual, it says that tightening it will turn off the light in a few days. It did turn off in 1.5 days but came back on the next day. Just hoping that driving with it loose did not do anything to any components of my car
Deal Fanatic
Jan 15, 2006
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Richmond Hill
Everything is fine. Might take a full tank till it clears. If you want to reset the light now, you can pull the ECU fuse under the hood. Just pull it out for 10 seconds or so. Should be labeled as ECU or pull the radio fuse and that should do the trick as well.
Member
Feb 23, 2013
499 posts
49 upvotes
NORTH YORK
EP32k2 wrote:
Dec 16th, 2012 10:22 pm
Everything is fine. Might take a full tank till it clears. If you want to reset the light now, you can pull the ECU fuse under the hood. Just pull it out for 10 seconds or so. Should be labeled as ECU or pull the radio fuse and that should do the trick as well.
I second that. You shouldn't have done any damage to the system at all. If pulling the fuse doesn't reset the light, have it scanned and see if there is something else wrong with it.
Sr. Member
Jun 21, 2006
617 posts
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check the cap gasket for cracks or if its worn if its ok have it checked out
commonly on those cars its the evap vent shut valve and charcol canister you have to change
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Jul 14, 2008
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Ontario
From my own experience, gas cap related check engine lights can be wonky.
I had this light related to my gas cap, even though mine is a capless system. First visit to mechanic they scanned the system and there was no issue with the engine. Apparently an issue with the part just inside the nozzle area - and I wasn't prepared to pay anywhere from $400 to $800 to repair what they THOUGHT it could be. After they reset the light, it came on again some time later, and this time, it registered NOTHING with the computer - so I had a check engine light as decoration on my vehicle.

About 1 month ago, I was going through a car wash, and I don't use the automated ones very often, and DURING the wash, the light left. Made me wonder if it had something to do with a dirty sensor inside or something (and washing with my own hose didn't clean it, whereas a high pressure one did, ???)
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Oct 5, 2008
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dlee89 wrote:
Dec 16th, 2012 6:51 pm
A few days ago, I left the gas cap loose (didn't click 3 times) and the check engine light came on. At that time I didn't know that it was because of that and drove from London to Toronto (2 hours) thinking I would get my mechanic to check it out, who happens to be in Toronto. When i got to Toronto, I checked and realized that it may be due to the loose gas cap. So I tightened the cap and drove it around normally. The check engine light came off about 1.5 days later. However, the next day it came back on. I was wondering if driving the 2 hours with a loose gas cap could have damaged something? Or will the light turn off permanently after awhile? I haven't put in a new full tank of gas either, thinking that it might be good to just use all the gas and then fill up with new gas for the whole tank instead of half a tank. Can anyone shed some light on my situation?

Either pull the fuse or unhook the positive battery terminal.....that will reset the ECU. If it comes back...get the code read OP. If it went back on, you may have a bad gas cap or something bigger.

Busybuyer888 wrote:
Dec 16th, 2012 7:08 pm
I recently, had a check engine light from a very under inflated front tire (I think)
Nope.

Maybe a TPMS light but there is no way a low tire threw a check ENGINE light.
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Oct 23, 2008
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Same thing kept happening with my wife's Civic. At first I thought it was because she wasn't tightening the cap because she only does one click instead of the recommend 3. Every time I would tighten it or fill up the tank the light would turn off but would sometimes flick back on when the tank was half-full. However, after she got her oil changed, the check engine light hasn't come on since.
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May 10, 2005
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Ottawa
dlee89 wrote:
Dec 16th, 2012 6:51 pm
A few days ago, I left the gas cap loose (didn't click 3 times) and the check engine light came on. At that time I didn't know that it was because of that and drove from London to Toronto (2 hours) thinking I would get my mechanic to check it out, who happens to be in Toronto. When i got to Toronto, I checked and realized that it may be due to the loose gas cap. So I tightened the cap and drove it around normally. The check engine light came off about 1.5 days later. However, the next day it came back on. I was wondering if driving the 2 hours with a loose gas cap could have damaged something? Or will the light turn off permanently after awhile? I haven't put in a new full tank of gas either, thinking that it might be good to just use all the gas and then fill up with new gas for the whole tank instead of half a tank. Can anyone shed some light on my situation?
Remove the cap, clean the seal on the cap and make sure the filler neck is clean too.
The CEL for gas cap is based on positive pressure. You need positive pressure int he tank to keep the sensor happy. It will go away and stay away soon. It may take a few days so don't worry.
Busybuyer888 wrote:
Dec 16th, 2012 7:08 pm
I recently, had a check engine light from a very under inflated front tire (I think). After filling all tires back to spec., the light went off the next day.

It is my understanding the only way to be sure is to have the onboard computer's error/diagnostic code be read, so you know exactly what it is unhappy about.

It is fine to refill the gas tank at any point.
No, a CEL light did not come on because of an under inflated tire....it is a check engine light. The CEL is not connected to your tires. Your intermittent CEL can be from anything like gas cap, to a bit of water in the gas or, engine misfire. The can all clear themselves.
You will get another indication for underinflated tires (if you even have tire pressure monitoring system installed on your car)
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Member
Nov 15, 2006
434 posts
30 upvotes
Just throwing this out there, my 9th gen civic displays a CEL if you overfill gas (eg rounding up to the next dollar when pumping)
The car thinks there's a large emissions leak even though the car is perfectly fine. Had this happen twice; dealers just reset the light after thorough diagnostics resulted in no issues. They chalked it up to a loose gas cap, which really wasn't the case.
Newbie
Dec 30, 2006
23 posts
1 upvote
My check engine light was on after I forgot to put cap back after filling the gas tank when the car is quite new. Since then, it's occasionally off and constantly back on. Technicians cheked and told not to worry so it's been on for many years. Corolla has this issues.
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