On Topic: Error Codes

Has anyone overfilled the gas tank recently to where it ran over and down into the drain holes? Gas cap has good seal, and on till it clicks a few times? I'm sure Ray O if lurking, would probably have a good idea of the usual culprits for those codes. If it's been overfilled recently, let it dry out. It will take a while. But if never overfilled, and the gas cap is good, you may have a problem with the EVAP system. IE: controls, pumps, canister, etc.

The Evaporative Emissions Control System is that which captures gasoline fumes and returns them to the gas tank. The first thing to check is the gas cap because it can be checked for free at many auto parts stores. If the gas cap is not sealing, then you can get errors that come up as GROSS LEAK and SMALL LEAK. The Purge Control can be affected as well as the Vent Control circuit.

I'm not saying the gas cap is definitely the problem, but it is free to check and cheap to replace and can be a factor in both of the error codes you have.

If the gas cap is not the problem, then you have to look to leaky hoses and a clogged charcoal canister.

P0441 is set when the pressure in the charcoal canister does not drop during purge control or during purge cut-off, the pressure in the charcoal canister is very low compared with atmospheric pressure.

P0446 is set when the vacuum switching valve ("VSV") for vapor pressure is off and the electronic control module ("ECM") judges that there is no continuity between the vapor pressure sensor and the charcoal canister or when the VSV for vapor pressure is on and the ECM judges that there is no continuity between the vapor pressure sensor and the fuel tank, or after the purge cut-off operates, the pressure in the charcoal canister is maintained at atmospheric pressure.

Both trouble codes use 2-trip detection logic.

Check for an open or short in the VSV circuit for the vapor pressure sensor, check the operation of the VSV for vapor pressure sensor, check for an open or short in the VSV circuit for EVAP (charcoal canister), look for vacuum hose cracks, holes, or blockage and for cracks, damage, or holes in the charcoal canister.

I believe that the VSV for EVAP is mounted on the charcoal canister.

You need a dealer quality tester to check for most of this stuff.

The evaporative emissions control system does not return captured gasoline fumes to the gas tank. Fumes captured from the fuel system are stored in the charcoal canister and are purged into the throttle body and burned in the engine.

P0441 and P0446 are NEVER caused by a loose, missing, or defective gas cap, and a loose, missing, or gas cap can not be a factor in either P0441 or P0446.

There can be a crack or hole anywhere in the system that upsets the purge pressure. Since you state that one would need a dealer quality tester to check this stuff, AND one can check a gas cap for free and buy a new one for around ten dollars if it leaks, then it only makes sense to at least check there first.

I happen to agree with you that this is likely to not be the problem, and that the charcoal canister and its plumbing is the more likely culprit, but when one can check a part that has a possibility, and do it for free in less than 5 minutes of getting out of the car, I think the part deserves at least passing attention.

I can't find the charcoal canister. It does not appear to be under the hood anywhere. I can't find any valves at Autozone for it. I only see one potential valve that I cannot identify that might possibly be bad.

I don't know where your canister is, but a typical installation has it inside a fender, in the "dead space" between the back of the wheel opening and the firewall.

Looked there in front and in back. It does not seem to be anywhere under the hood.

This video on the subject is very good:

I've seen them where you must remove the fender lining and get at them from the tire-side of the fender. I've also seen them hiding inside the fender, behind the headlamp.

The point is, it has to be there someplace.

Very good. I like it.

And, the canister is not hiding inside a fender, it's hiding over the rear axle.

Ed's link showed it above the rear axle. Also a $300 part even though there are multiple accessible parts that *could* have been sold separately :(