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So I had a 'Check Gas Cap' light come on the other day, and I must have tightened the thing down 100 times afterward. So I pulled out the Predator today and read the engine code that popped up this morning and noted something about the cap being loose/off. So I cleared the code and it hasn't come back yet. But it seems like the previous code I cleared hasn't come back either. Is it something wrong with my car that it won't clear codes by itself? I'm getting the jitterbugs because I'm worried I have a car that's falling apart right before I put 6k Into a KB Supercharger.
 

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I don't know if it makes you feel any better or not but I get that one about once every couple of months. I've had it in and they inform me it's a computer glitch and it doesn't really mean there's a problem. Seems to me it's like a P0442 or something like that, there's two code numbers I think. I too just clear it and keep going!
 

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Got that on my wife's Taurus.

Kept coming back after I cleared it.

Spending $12 on a new gas cap ended those shenanigans.
 

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The check gas cap light is triggered by a P0442 "small evap leak," and while most commonly that is in relation to the gas cap, it can be caused by any small leak in the evaporative emissions system. It doesn't cause any driveability issues, but it won't pass inspection with a code in memory (at least in Mass). It used to turn on the check engine light (and still does on some vehicles), and I guess too many people got freaked out by it.
 

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If the cap was indeed loose (and not defective), the light will eventually go out and the computer will reset itself. It takes a certain amount of "driving cycles", which consist of starting the engine from cold and bringing it up to operating temperature. I'm not sure of the exact details on Fords, but it has to be at operating temperature for a certain amount of time. Then, the computer will run tests, and after a certain number of successful tests, it will turn the light off. If you Google "emissions testing", you can get the exact details.

I learned a lot about it after having the issue with my wife's 300M. I ended up removing the gas tank and replacing a 2" piece of 1/4" vecuum hose. That $.25 piece of hose would have cost me $1,000 at the dealer.

Bruce
 

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For a Ford to clear the evaporative emissions monitor, it needs to be driven at consistent speed and on a straight road (basically no fuel sloshing) for 10-15 minutes between 1/4 and full tank (full being more preferable) at a temperature of 60*F or higher. That's the hardest monitor to reset as part of a driving cycle. But that code will still be stored in memory, so I suggest having the codes cleared at an AutoZone or the like.
 
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