Check Fuel Cap Message

[AcidKoolz]

I have been getting a check fuel cap message on my 05 GT. I see that this is where the fuel take cannot create a vacuum, IE a leak, usually through a not properly closed fuel cap. Obviously I have ensured my fuel cap is properly closed, any ideas?

[stang man]

I have been getting a check fuel cap message on my 05 GT. I see that this is where the fuel take cannot create a vacuum, IE a leak, usually through a not properly closed fuel cap. Obviously I have ensured my fuel cap is properly closed, any ideas?


Just disconnect the negative terminal on the battery for about 2 minute then replace it. This should reset the code that you are getting. If that doesn't work you may need to replace the cap and/or the sensor.

[AcidKoolz]

Already tried clearing it to no avail, just comes back on after awhile....Might try replacing the cap. Speaking of clearing codes, my car is throwing a CEL for 02 sensors, and I am going to get an O/R X pipe soon.... anyone know where I can get some MIL Eliminators for the 05+? They seem to be very hard to find, and I have read a few things on other forums about how they weren't really made for the 2005+....any input?

[adam2kgt]

The cap will probably need to be replaced. As far as the off road pipe, plan on getting a tuner with the rear O2 sensors turned off, because nobody makes MIL elims for that year, as far as I know. Plus, you will need to tune for the extra airflow anyway.

[ArkansasMystic]

Not sure on the newer cars, but I used some spark plug non foulers in my 96 to get rid of the check engine light. If you end up needing something like that, let me know and I'll dig up the thread.

[adam2kgt]

My dad tried running non foulers in his 07 with an off road pipe, and it wouldn't keep the light off.

[ArkansasMystic]

Hmm, it's possible something changed over the years, but worked like a charm on mine. Also, you can build you own MIL eliminators for pretty cheap.

[Bigjht]

I don't see any exhaust mods in your list so I'm assuming it's stock? Assuming that I think the thing to find out first would by why is it throwing an O2 sensor code? It could be just the sensor but it may be something else. Is it running different than when it wasn't throwing a code? After that I would recommend just getting a tuner and turn them off plus you will see great gains that will really bring your car to life. It's a win-win.

[stang man]

I don't see any exhaust mods in your list so I'm assuming it's stock? Assuming that I think the thing to find out first would by why is it throwing an O2 sensor code? It could be just the sensor but it may be something else. Is it running different than when it wasn't throwing a code? After that I would recommend just getting a tuner and turn them off plus you will see great gains that will really bring your car to life. It's a win-win.

+1. It sounds like you have some problems that need to be addressed.

[AcidKoolz]

Hmmm.... I had assumed o2 sensors....but maybe not.

Codes it is throwing:

P0420 Catalyst System Bank Efficiency below Threshold - Bank No 1.
P0430 Catalyst System Bank Efficiency below Threshold - Bank No 2.

It was throwing this one too:

P0506 Idle lower than expected

but that one stopped after I cleared them, and hasn't came back yet, however I haven't read them lately so not positive.

What else would this be? I don't see any leaks....sometimes it smells like the car is running a little rich...Maybe a clogged cat?


Bigjht - it doesn't seem to be running any differently, although I didn't have it long before it started throwing the codes...so I'm not entirely positive. It doesn't hesitiate or anything....just smells like gas. That might have also something to do with fuel cap msg? Maybe a leak in the neck of the tank or something, ergh...

[stang man]

Hmm. Running rich indicates its in limp mode doesn't it? Whats your fuel mileage like?

[abdullaGT]

Bad o2 sensors can cause it to run rich, your best bet would be to replace them and see how that goes, or have your cats checked.

[AcidKoolz]

Fuel Mileage is around 15.5 combo of city/hwy.

So Today I got in to go to work and battery was dead...awesome. Nothing was left running or on, and the battery is new.

Charged it up, and it started fine....When I get to work and pull into the parking lot, I pushed the clutch in and the car died....

Has ran fine ever since. lol

[stang man]

15.5??? Thats terrible! I get that with a JLT cold air intake and a Bama chips tune. Do you have any mods on the motor?

As far as your battery, is your alternator charging? If it is, then I have seen brand new batterys go bad..

[Bigjht]

Is the MAF sensor a possibility as well? If it's dirty or malfunctioning could cause it to add more fuel than needed, causing the code and possibly fouling the O2 sensor? I know it could cause a low idle and could've caused the car to die when you pushed the clutch in while pulling in the parking lot, had that happen a few times on my 99 when I was having MAF issues. I don't know if this is the issue, just throwing out possibilities. You may want to try cleaning it just in case, cheap and easy.

[stang man]

That reminds me, I need to clean mine before Branson...

[abdullaGT]

hmm, if you may want to have your alternator tested, it could also cause other codes to show up.

[AcidKoolz]

hmm, if you may want to have your alternator tested, it could also cause other codes to show up.

Alternator test returned 14.3volts...I think he actually said 43 but that sounds riduculously high. Maybe I misunderstood. 14.3 would be about right, he said the alternator tested fine.

Still throwing both O2 codes, nothing else. I cleaned MAF, TB, and air filter a couple of months ago, I guess it wouldn't hurt it to do it again. Also seafoamed a couple months ago. Anyone else use that here? That stuff is amazing.

No mods on the motor yet, still stock. I was thinking of just getting my off-road x in place of the o2 sensors, since they are about the same price. Then I guess I will need a tuner to shut off the o2's.

I love tracking down problems....