"Check Engine Light" Mystery, It appears only to suddenly disappear... Options

[TheRockman]

OK, here's the deal. This past Sunday while driving home I get the infamous "Check Engine Light". My odometer had just rolled over to 139,149 miles. I mean just clicked into that mileage and the light turns on. SURPRISE!

So I'm thinking, "Oh crap here it goes. Here's where the engine becomes a cranky old man." But this morning, I'm driving to work and the light turns off! Nothing! Again, the odometer had just clicked over to 139,234 when this happend.

So good news: Check engine light is gone. Mystery: Why did it come on in the first place?

I know that my Dad's old Dodge Caravan would turn on the check engine light at about every 50,000 miles (which was crap) and that was the first thing that came to mind about this situation.

I'm going to get the car checked out Friday and see if any codes were stored or if it's still throwing some sort of trouble code without the light.

In the mean time, does anyone have any ideas about what might be going on? Has this happened to anyone?

[alltracman78]

IIRC PO446 is a small leak.
You probably left your gas cap a bit loose.
That or the sealing surface is slightly corroded.

When you tighten the gas cap, ALWAYS make sure it clicks.
And hit up the sealing surface [there's a seal on the cap that seals to the metal ring of the fill tube] with some FINE sandpaper, to clean off any corrosion.

There is also the possibility the canister or a hose, but they are less likely.
If you do both of the above and it still comes on, take a look at the hoses and such.