So I've been getting an intermittent Check Engine light on my 2002 PT Cruiser for the past few months. Usually it would go away after a few days; this time, it stayed on for good.
Running the Ignition on-off-on-off-on-off-on-off-on sequence gave me the error code P0456, which translates into "Evap Leak Monitor Small (0.020) Leak Detected."
I was hoping it would go away, but it didn't. I noticed fuel economy had gotten a bit worse. I checked the gas cap was tight, though it's my understanding that a loose cap would set code 455, for a "Gross leak," not the small leak that was indicated here.
Dammit, now I have to pay a professional to find the problem; I don't have the skill or equipment for this one. They hooked up the computer, got the same code. So they did a smoke test, and found a moderate leak around the gas cap and filler neck area.
It wasn't a loose gas cap, it was a BAD gas cap -- the seal apparently had just worn out or something. New cap, reset the computer, and all is well. They re-did the smoke test, and it was fine.
So if anybody runs into that code, it might be worth trying the $12.00 gas cap *before* the $75 in diagnostics. But overall, I was surprised at how cheap I got out the door at around $90, and got two recalls fixed while I was there. Nice.