Diagnosing EVAP system codes P0442 and P0456 (2 Viewers)

[jOnathN]

FWIW you probably did not need the charcoal canister. Code p2418 (evap switching circuit open) is supposedly the canister-mounted valve. Just fixed that on my 2004 a few weeks ago. OTOH, if you have high miles you would have needed one eventually anyway.

Anyway, p0456 is “EVAP system small leak”… which could be a lot of things. On the plus side, most are easy to fix:
1) gas cap - try a little gasket dressing on the rubber sealing ring. I use Hylomar HPF but there are plenty to choose from. Press and turn to seal… mentioned since about every second time my wife fills up the light comes back and I have to go tighten the cap.
2) 25860-50100 vsv near engine intake. About $90 and ten min to change; hangs off the intake plenum.
3) 25860-50150, second vsv near engine - not sure every model year has this one. On mine it’s on the DS between the battery and brake booster assembly. Also easy to change
4) fuel filler neck. Especially if you have rust, could be pinholes in the neck. Not sure how difficult (or easy) this is to change.
5) 77740-60440 canister assembly - comes as a unit with two valves and some hoses. If you replace any one thing there, just replace the whole unit so you don’t have to chase the problem around. Takes 15 to swap: 3 bolts, 3 hoses, and one connector. All easy to reach after you drop the spare.
6) any of the vacuum hoses between the canister and intake. There are three short elbows at the canister and a few more running up to the front (for my 2004 anyway).

Part numbers for a 2004 LX.

Good luck!

(YMMV, IANAL, etc)

 

[fluffyrae]

Then I don't think the air intake hose matters, because the evap system is a closed loop outside the air intake. The loose air intake would more likely trigger a lean fuel mixture code. So my guess is that the p0442 is an entire new problem, but could also be due to a lose or broken vacuum hose which are close to the valve covers and can be damage due to being brittle. This is my insight but also my first car with this system (diesel guy).

Just to close this out, I started having issues starting (either slow to turn over or not at all). I checked all the vacuum hoses again for leaks and connections. I followed the diagram on the underside of the hood and lo and behold, my mechanic switched the hose that terminates at the throttle body with the one that terminates in the airbox assembly. Having been under the hood a million times I just felt like the hoses weren’t seated correctly on visual inspection. In any event, that seems to have solved the issue. Cleared the code and we will see what happens.