I have a 2000 Mustang GT. I replaced gas cap still have same problem as anyone else had this problem and how do you fix it?

 

Drive the car. What I mean by that is the computer needs to recalculate and it will take a few miles for this to happen. I'm not positive on the Ford side, but my Chevy truck needed to be driven. The short trips locally didn't provide enough time for it to recalibrate, but a longer trip cleared the error.

 

Some cars need a minimum number of good trips to reset a code. On my GFs Caliber, it's 3, don't know what it is on a Mustang.

 

I use a Scan Gage II for the various extra gage functions ..... as well as to read and reset codes in several of my vehicles if and when they pop up.

I dealt with this very deal one day in my 2007 F150 FX4.

Just started it up and that warning kept coming on, in spite of my checking the cap and knowing it was good. We were taking the truck to Roanoke to get some stuff and I thought maybe it would reset itself, that maybe that was a code the SGII couldn't reset ?

Stopped a few miles from home to get gas and a cup of coffee and then when I got out, I could smell gas. Had a small drip from fuel tank area behind cab in front of bed. Slid under the truck to look / feel above tank at lines, small high pressure line had a leak at a pin hole but fuel pump was pumping enough to supply .... but the reason for the "check gas cap warning" was the fact that about 5 inches of the larger vapor return line was eaten away all along the top side.

At least I could drive the truck still and wasn't stranded.

So I took the truck home, drove car for our shopping ride, stopped by at Magic City Ford, found out new lines were near $300 (and they had NO guarantee against rodent damage).

I figured out a better way to resolve the issue using some adaptors and copper and then shielded the lines where it looked like a squirrel had sat on top of the tank and ate into the return line that is dry .... and looked like he tried to bite the high pressure fuel supply line and as it was under pressure, likely stopped when he got a shot of gas in the face.