Endless Evap/Emission codes headache

[u/Wanna_make_cash]

2013 Subaru Legacy P0456 Code

This car has been nothing but an emissions/evap system headache.

Over the last year and half, it's had intermittent emissions, vacuum, and evap related codes. The exact codes and repairs varied based on when in time we are talking about. Memory seems to bring up p0441, p0442, p0420 and p0171, though this may not be correct and is a recollection across several past repairs over the last year and a half.

Long story short, over the last year and a half chasing a variety of emissions and evap codes ,the purge valve was replaced twice, the charcoal canister was replaced, and we had to get a new catalytic converter. Each repair worked on its own for a short time, but then a few months would pass and a new code would pop up with a new repair. Eventually, everything was chill for several months at the point when everything was said and done, and it was a glorious time of no lights.

Now, the light is back. This time, it's a P0456 Code. What could it be this time?? I swear by the time we're done with this car, every single component is going to have been replaced 3 times over just to pass a stupid emissions smog test to legally register the car every other year.

Half the people say "it's always a gas cap" half always say "it's never the gas cap, it's probably a purge valve or charcoal canister or a hose". Then half the people say that the p0456 "very small" leaks can be an incredibly difficult thing to find, even for actual mechanics with smoke machines

I'm just hoping whatever's broken or has a hole isn't too expensive to fix. This dang emissions and evap system has been so costly between all these parts breaking. So much money spent just to make sure I can pass a stupid smog test.

I've seen stories with this code specifically where it can drastically range from just a $20 gas cap, all the way into more than a thousand dollars for a new gas tank because of a tiny tiny pinhole somewhere that can only be fixed by changing the entire component out.

[u/Chippy569]

P0456 is a "small evap system leak detected" code.

While that could be a leak anywhere in the fuel system, the most common places are up by the filler neck (gas cap's gasket or rust on underside of pipe), damage to the hoses that run on top of the gas tank, or damage to the hoses in/out of the charcoal canister up above the rear diff. There isn't a great way to diagnose these, but a smoke machine is the best bet. Without knowing where the leak is, obviously no one can tell you how expensive it will be

Rubber things degrading is kinda the nature of owning a 10+ year old car.

[u/Wanna_make_cash → u/Chippy569]

Fair enough. At least it isn't a majorly urgent concern to like fix right this second kind of issue. Gonna have a shop look at it as soon as we can though in the next week or two. I just hate the anxiety that seeing the stupid engine light gives me and thinking about the worst case scenario repair cost every time I see it.

I'm just frustrated that so many component of the system seem to be having issues in relatively close proximity. A charcoal canister, a catalytic converter, and 2 purge valves in a year is a lot of parts going bad

[u/hambonelicker]

Did you get the evap canister by the gas tank replaced? That was the issue on our outback and it was easily diagnosed but not easily repaired.

[u/Wanna_make_cash → u/hambonelicker]

Is that different than the charcoal canister?

[u/hambonelicker → u/Wanna_make_cash]

Probably, I’ve always know it as an evaporative emission system canister. It does have some charcoal and several valves that eventually stop working. It’s a pricey fix for an inexpensive part.