"Check engine" light

I had written before about my problem with my check engine light being
on. The code that showed was P1456 Code is "EVAP emission control
system leak detected".

It had been to the dealer 4 times, tested each time. The first time,
they recommended a new gas cap, which I got. Then, the other times,
they "smoke tested" the thing, and they ended up saying "I don't know
what's causing this...all of our 'smoke tests' passed".

Now, all of a sudden, after being illuminated for about the past 3-4
weeks, it went off, just as mysteriously as it came on. At first I
thought the bulb had burned out, but no, when I started up the engine,
all the little dashboard lights were properly on. It wasn't that.

Some friends have suggested that the cooler weather may have had
something to do with it. I'd agree with that, except that the day it
disappeared, the outside temp was around 85F.

I'm beginning to think that the "check engine" light is like Chicken
Little shouting "The sky is falling!" (or, perhaps, the boy who cried
"wolf"), and I'll be much less likely to be overly upset at its lighting
up again.

 

Never replace the gas cap unless the DTC is P0457.

Year and model of vehicle? Some have specific issues not shared by others.

That complicated EVAP isn't really important except to the bureaucrats who
dictated that cars should have it in the first place.

A P1456 DTC /does/ indicate that there's a problem of some kind on the tank
side.

Need year and model first, though. Plus whether it's V6 or 4.