EVAP help


#1

I have a 2003 Toyota Tacoma 4wd with a 4cyl 2.7 liter engine. I have been throwing the following codes for awhile.
P0446 (Evaporative Emission System Vent Control Circuit)
P0441 (Evaporative Emission System Incorrect Purge Flow)
P0442 (Evaporative Emission System Leak Detected)
the P0446 is then repeated a second time

I understand something is wrong with my EVAP system meaning the gasoline vapors are not being fed back into my system because of a leak or a bad purge/shut valve, etc. I have replaced the gas cap and inspected the lines visually for leaks.

I am hoping that with the specific codes, and the information that I only throw the codes when the temperature is above 50 degrees, that someone can point me towards the most likely problem or tell me how I can test the valves without paying for a smoke test. I read something about using a multimeter to trip the valves open and closed, how can I test if they are doing this correctly.
Thank you for any information!


#2

These codes mean the vapor canister needs replacement. Fortunately Toyota supplies the canister with all the small parts that make it work so you don’t need to buy anything else such as vent valve solenoid or pressure sensor.


#3

Darn!
I was truly hoping that was not the case! The canister is above the fuel tank, I may have to drop the whole tank to get to it. No fun.


#4

@thecaps I don’t think you have to drop the tank because the book time to replace the canister is only .4 hours.


#5

Wow talk about a leap. On my '02 I got the same codes because of a vacuum hose to a valve on the air filter housing I forgot to reattach. These codes DO NOT automatically mean the charcoal canister is bad. It very we’ll may be bad, but get some other input. Check for the easy things like vacuum hoses, and electrical connections, and operation of the vent and purge valves, before just replacing the most expensive part of the EVAP system.


#6

That pile of codes can mean a lot of things. It could, for example, just mean that you have an evap hose leak - in particular, back in the area of the canister & vent valve. If there is a leak, it messes up the pressure readings that the PCM uses to test things. Especially given the P0442, I would simply investigate that first.

The vent valve itself can be tested. You can check that it receives power (probably 12V), and can directly energize the valve itself. But, in general these things are very difficult to diagnose, and a new canister is a pretty expensive guess. Simple visual inspection is a good place to start.


#7

All good advice. I’d hate to replace the canister without knowing for sure that it isn’t a valve or hose leak. Sounds like my best bet is a smoke test. Anyone know what a good rate is for that test? I asked for a few quotes and heard anything from 85 to 150.


#8

Smog shops that specialize in emissions repair will usually charge in the lower end of the range. Typically you see prices around 100 dollars for an evap leak check.

Pay close attention to the fuel filler neck. They typically get rusty where the plastic and metal combine near the top where the gas cap is.


#9

I will do that. Thanks!