Intermittant Gascap Error

[Paul M]

Started the Jeep (2007) and the "gascap" diagnostic indicator came up in the driver display with the ding sound. I tightened the cap...no change. Re-started...still sounding off. Cap doesn't seem loose or faulty. Anyone know what the problem may be?:hmm:

 

[Luke]

The rubber on the cap still intact? ie good seal?

Do you have an error code too?

 

[Paul M]

I'll check the seal tomorrow thinking too many rough roads and dust may have compromised it. No error code. OM suggests the gascap notification is either a loose cap and needs tightening, or damaged and needs replacement.

 

[Hedsic]

I take it not all KJ's have this? I forgot to put my gas cap back on once so it was dangling there with the gas tank door open. Was a long day and I was exhausted. I noticed it while driving and figured it wouln't be a big deal since I was only going 15 miles or so. Never got an indicator or anything though.

 

[Luke]

It must be an '07 warning ... I just get an error code (if anything). My money is on a new cap. :waytogo:

 

[Paul M]

Took the cap apart, cleaned it, put all the components back together...rats, same error indicator. Two things: 1) might disconnect the battery to see if that resets the computer, or 2) may need to break down and buy a new cap, which is wholly bogus.

Small rant: This failure is incomprehensible. What vehicle requires a new gas cap from normal use at 120K miles? How lame could the designers possibly get to create a complicated fuel filler cap that ultimately fails (the thing has 11 parts)? Idiotic if you ask me.

 

[tjkj2002]

Took the cap apart, cleaned it, put all the components back together...rats, same error indicator. Two things: 1) might disconnect the battery to see if that resets the computer, or 2) may need to break down and buy a new cap, which is wholly bogus.

Small rant: This failure is incomprehensible. What vehicle requires a new gas cap from normal use at 120K miles? How lame could the designers possibly get to create a complicated fuel filler cap that ultimately fails (the thing has 11 parts)? Idiotic if you ask me.

Emissions....................

You have a vacuum pump to test the EVAP system and the gas cap is part of said EVAP system.They started to add a "gascap" light for the P code for very small EVAP leak which 90% of the time is a bad gas cap.Without that "gascap" light you will get the check engine light turned on.


It can take several days,even weeks before the PCM runs the EVAP monitor so you could run for a day or 2 without a gas cap and no light depending on your driving and if it meets the requirements for the PCM to run the EVAP monitor or not.


The gas cap is not longer just a gas cap and they do fail more often then older vehicles.I just swap in a new OEM gas cap once a year,costs like $15 and never have to worry.

 

[Paul M]

Emissions....................

You have a vacuum pump to test the EVAP system and the gas cap is part of said EVAP system.They started to add a "gascap" light for the P code for very small EVAP leak which 90% of the time is a bad gas cap.Without that "gascap" light you will get the check engine light turned on.


It can take several days,even weeks before the PCM runs the EVAP monitor so you could run for a day or 2 without a gas cap and no light depending on your driving and if it meets the requirements for the PCM to run the EVAP monitor or not.


The gas cap is not longer just a gas cap and they do fail more often then older vehicles.I just swap in a new OEM gas cap once a year,costs like $15 and never have to worry.

Who'd a thunk it? Even as an engineer- type still seems a little odd. I'm still a little baffled as to what exactly failed in the cap? The breather? The seal? No matter, worth a new one after too many rough roads. Thanks to everyone for their insight/suggestions.

 

[Paul M]

Bought the new cap online, $11 shipped. Anyone else find it's always a quandary whether to spend valuable time attempting to repair the original, refusing to believe it can't quickly be fixed, or forget about it and breakdown for a replacement...overcoming the pain of tossing the old one into the can.

 

[Porkchop]

Or just read were someone replaced the front drive shaft only to find out they could have rebuilt the CVs on it. Now there's a quandary for ya in reverse at about $300.00 not $11.00. Ouch

 

[Paul M]

Or just read were someone replaced the front drive shaft only to find out they could have rebuilt the CVs on it. Now there's a quandary for ya in reverse at about $300.00 not $11.00. Ouch

Yeah, I get that though. Altho, rebuilding assemblies that are assumed will wear out is worth it versus straight out replacement. I guess in the end my question wasn't realistic...ya can't look at it as time not well spent...it's not about the hours involved or saving money. There is a great satisfaction in fixing or upgrading your ride, even if that means ordering something simple like a replacement fuel filler cap (which has the added benefit of stopping the annoying gascap fail ding.)

 

[Atrus]

It can take several days,even weeks before the PCM runs the EVAP monitor so you could run for a day or 2 without a gas cap and no light depending on your driving and if it meets the requirements for the PCM to run the EVAP monitor or not.

Good to know. I filled up on Sun or Mon, drove the KJ a few days, and then it sat in the garage a few days. Friday, fired it up and got that message. Gas cap was loose. I couldn't understand how anyone could have tampered with it, but was concerned since I drove it for a few days with no light - in my mind, someone had to have messed with it. Seems like your explanation works - the PCM isn't continuously monitoring for it, so it didn't flag me. I probably didn't tighten it down properly.

 

[Paul M]

Okay, new thought...since the fuel cap is integral to the EVAP system and the PCM only monitors intermittently, and possibly my cap either has failed or was not 3-clicks tight when the last EVAP monitor session initiated, I'm thinking I should drive the Liberty around for a while (been using the pickup lately) hoping the PCM checks the EVAP system, finds no fault, then resets the indicator. Is there a way to force a EVAP monitor session?

 

[tjkj2002]

Is there a way to force a EVAP monitor session?

Yes but that actual test cycle info is at work.It is a drive test that starts out with the coolant between 2 set points,the rpm's must reach a certain range,the distance goal must be met,the coolant temp must reach a goal also,and many other preset goals must be met.It's tricky and a 20-30min process.1st though to make it faster you must clear the stored monitors which makes the PCM look for a valid test cycle quickly.


Same reason why resetting a check engine light(clearing any codes) right before a emission test will always fail you since none of the monitors have been run with a pass/fail readout.

 

[Paul M]

Sounds complicated...thanks for the intell. What about pulling power for fifteen minutes then driving around for a bit?

 

[tjkj2002]

Sounds complicated...thanks for the intell. What about pulling power for fifteen minutes then driving around for a bit?

They can be but yeah pulling the battery cable then driving for a good 30mins in both stop and go and highway you should get a trip done.Just start out with a cold engine but with the outside temps above 50 degrees.

 

[Paul M]

I'll give that go...never know, might reset the PCM.

Oh, and I meant pulling power for 15 minutes, reattaching power, then driving around. Hehe

 

[Paul M]

New cap, all good. No check engine light or gascap alarm. That simple. Although initially I did put the new cap on only to stiil have the error. So I pulled power for about fifteen minutes. Thereafter the check engine light went off, apparently resetting the PCM fault. Not sure if pulling power first on the old cap would have done the trick, but no matter, the new cap is better (1-click vs 3, hehe), atho no keeper attach hole. Oh well, can't win em all, always fell off anyway.