P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
The evaporative emission control system checks to make sure there are no leaks in the lines that run from the gas tank to the charcoal canister and up to the engine. It also checks to make sure the gas cap is sealing correctly.
When you fill your car with gas, the vapors in the tank get forced into a canister filled with activated charcoal. Also, on a hot day as the gas heats up and vaporizes, those same vapors push into the canister where they’re stored. But the charcoal can only hold so much vapor. At some point it has to be emptied. The emptying process is called “canister purge.” Here’s how it works.
The computer orders a canister purge by powering open a purge solenoid. That opens the vacuum line between the canister and the intake manifold. At the same time, it opens a VENT solenoid. That allows fresh air into the canister. So the engine is literally sucking out the gas vapors and purging the canister with fresh air. The computer has to adapt its fuel strategy to take advantage of all the extra gas vapors coming into the engine.
The computer notices the canister is empty when it detects a leaner condition (all the vapors are used up) and it resumes normal fuel delivery. Some car manufacturers then close the VENT solenoid but leave the PURGE solenoid open. That creates a vacuum throughout the entire fuel storage system. Once the correct vacuum is reached, it closed the PURGE solenoid and waits to see if the vacuum holds. If it doesn, the system passes the test. If it detects a leak, it sets a code.
The computer also watches the electrical activity during the testing process. When the computer operates the solenoids, it sees a voltage drop on the line. If it doesn’t see a voltage drop, it knows there’s a problem with the electrical–either the wiring is broken, or the solenoid isn’t working. In this partcular code P0446, the computer has detected an electrical problem with the VENT solenoid.
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© 2012 Rick Muscoplat
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so, is the PURGE and the VENT all in the same solenoid? Because i’ve found TWO “purge” solenoids on my car. The one by the intake manifold and the other in the rear wheel well that is connected to a big charcoal canister by the gas tank. Which of these “solenoids” is the problem with a P0446 code?
Rule #1 when asking a car question—Year, Make, Model, and Engine. Most cars have a vent solenoid and a purge solenoid. Since you didn’t tell me what vehicle you own, I can’t tell you which is which.
Amy
The vent valve is down by the charcoal canister and the purge valve is up next to intake manifold p0446 is talking about the vent valve at canister.
i have a 1999 Toyota corrolla CE. I got that engine error P0446 Evaporative Emission Control System Vent Control Circuit Malfunction. i need to know how do I fix the issue without taking it to a garage?
i have a 08 shelby gt 500 that goes into failsafe mode and throws the p0446 code, and i have replaced the solenoid under the rear end, and that was no help waht should i be looking at??
whats ups?
You’ve got two solenoid valves in the evap system. One is the purge valve, the other is the vent. This code P0446 refers to an electrical problem in the vent valve. I don’t know which one you replaced. So you need to run tests on the connector first to make sure you don’t have a short in the harness. Then test the resistance of the new valve. If it tests good, you’ll need to test it again for voltage drop when powered up. Did you replace the solenoid with genuine Ford? Some shops are report repeat failures on these solenoid valves. If yours fails, the parts store should replace it under warranty.
yes Rick it was a Ford part, and it tests out ok, but still have the code under high boost
I have a Saturn SL1 2001 with P0446 on it. Where can I take it to get the repair done without spending too much.
Thanks,