Check Engine Light Went Off By Itself?

I have a 2012 Ford Focus 84,000 miles.

Last week I had to take a trip and stopped to fill up the tank. On the way back, my check engine light went on with the code P0420. I took it into the Ford dealer and they said they need to replace my Vapor Management Valve, Fuel Tank, Cat Converter and Gasket… $2195 repair. They said the VMV caused this.

Last night, I had to take another trip. Filled my gas tank up at a my normal place. Drove. No issues with driving.

When I go to start my car back up today, check engine light is no longer on. Car runs fine. It IS raining out a lot if that means anything.

Any thoughts if this could be bad gas, malfunction, etc. Why would they need to replace my gas tank? That doesn't sound right…

Should I just chaulk this up to some bad gas?

When you fill with gas, do you top it off after the nozzle clicks off? If so, this could be the problem. The VMV periodically purges the fuel vapors out of the fuel tank filler neck. If over-filled, the valve will malfunction causing the check engine light to come on. If it is successful the next time it tries to purge, the light will go away. Don't fill past the auto shut off point of the fuel nozzle and you shouldn't have a problem.

Chevy dealer replaced my gas cap and took care of the check engine light. They said it has to do with the pressure in the gas tank? It may just be you tightened the gas cap right.

False code for a failed cat converter. It might come back.

The old P0420 code? Lol, that has made repair shops more money for doing nothing. It could be one of these items… The O2 sensors, the MAF sensor, the Cat, the Cat gasket, the spark plugs, the spark plug wires, cheap gas, an oil change, a cracked exhaust pipe, a leaking intake gasket, a cracked intake manifold, a stuck PCV valve… The list goes on, but of course the dealer will 'fix' the problem, starting with the most expensive first. You, on the other hand, can start with the cheapest. #1, get a second and even a third opinion, then start with the easy stuff.

This is a disturbing estimate isn't it. The light went off because the computer ran another test and the car passed. Find an other place to take your car. This place is not right.

It will come back. Like my mechanic says, it's like a recording.

The P0420 code means that the Bank 1 converter is not meeting the minimum requirements to reduce emissions in the exhaust. It won't hurt anything to drive it that way but you won't pass an emission test to get your plates renewed if the light comes back on. I'd go to a muffler shop that handles "Walker" brand after market converters. The rest of the things you listed I'd not be concerned with unless the CEL lights up and you have specific codes for those items. I'll guess a Walker converter is under $300 and another $250 to $200 to install. That $2195 is a joke.

Chalk it up to a Faulty sensor

You probably never put the fuel cap on correctly. You can't blame the main dealers for trying to bulk the job out. They have big shiny showrooms to pay for.