If you’re getting a P0446 trouble code on your OBD-II scanner, read on to get an idea of what this means, what may have caused it, and how you can diagnose and fix it.
Code P0446, otherwise known as Evaporative Emission Control System (EVAP) Vent Control Circuit Malfunction, indicates that your car’s computer has detected (or believes it has detected) a problem with the function of the EVAP system vent valve.
Your car’s computer controls the vent valve (it also controls the purge valve). Additionally, the computer monitors the valve and its control circuit for problems. Code P0446 sometimes indicates that an electrical failure has been detected in either the vent valve itself or its control circuit.
While the P0446 can indicate an electrical problem on later model Fords, which, for some strange reason chooses to look at the vent valve electrical circuit to set this code, the P0446 code is highly unlikely to be an electrical concern on other makes. GMs and older Fords would set this code when the canister wouldn’t vent after the EVAP test, and in those cases, this code is far more likely to be triggered by mechanical clogging.
Do note that code P0446 appears more commonly on older vehicles, usually from domestic manufacturers like GM. Dodge hasn’t listed the code for a while, and models like the Toyota Camry also haven’t listed the code since the 2007 model year.
The code appears in a 2005 Toyota Camry 2.4L because of the following conditions:
Since there are varying descriptions of the P0446 code among car manufacturers, the possible causes can differ depending on the make and model of your car.
Here are the most common causes of an EVAP System Malfunction or code P0446:
Code P0446 is set when the car’s computer believes (either correctly or incorrectly) that there’s a problem with the vent valve. Some systems use vacuum pressure readings to judge vent valve performance. As such, in some cases, parts that might surprise you can trigger the code. Examples include:
In a Lexus and Toyota, the code P0446 may point to a failing vacuum switching valve. This problem is very common to models from the two Japanese marques.
Anomalies in the EVAP system often come with symptoms that you shouldn’t ignore. Below are the signs you need to look for if you get a P0446 code on your OBD-II scanner.
P0446 can be a serious issue. All potential causes must be looked into to come up with the correct diagnosis. Consider taking your vehicle to a professional automotive technician if you don’t have enough DIY auto repair experience and skills. However, if you still want to take a stab at the diagnosis process, the videos below can help you do it correctly.
There are multiple reasons why code P0446 might be stored. Therefore, there isn’t a “magic bullet” fix for the issue. You’ll need to diagnose the code accurately, as outlined above, then perform any necessary repairs.
Also, keep in mind that all vehicles are different. When troubleshooting and repairing diagnostic trouble codes, you should consult the factory repair information for your application.
Repair manuals, such as those from Chilton, are useful, but an ALLDATA subscription is even better. ALLDATA has single-vehicle subscriptions for DIYers that provide detailed factory repair information.
P0446, in general, is a trouble code that’s difficult to pinpoint right away. You will need to perform a series of extensive diagnoses to get to the problem.
If you have an advanced scan tool at bay, you can use it to diagnose the P0446 code and get real-time powertrain control module data. This tool can also enable the vent and purge to turn the solenoid on and off to tell you where the leak is coming from.
Basically, the EVAP system is a collection of components working together to prevent fuel vapors from entering the atmosphere. Although system designs vary, typically, the primary components found within an EVAP system include the gas tank, the gas cap, the vent valve, the purge valve, and the charcoal canister.
When the engine is off, fuel vapors are stored in the charcoal canister, rather than escaping into the atmosphere. Once the engine is running and the appropriate conditions are met, the purge valve opens to allow the vapors to enter the engine, where they are burned during the normal combustion process.
The vent valve, which allows fresh air to enter the charcoal canister, is usually open. But when your car’s computer wants to check the EVAP system for leaks, it commands the electronically controlled vent valve to close, thereby sealing everything off. Then, the system can perform its self-test.
As described earlier, the vent valve is normally open, so an electrical problem won’t typically generate a P0446 on most platforms. The vent valve will remain mechanically open in those cases, which will vent the canister all the time – setting a different code, such as a P0455. The P0446 is more likely to be a mechanically stuck closed vent valve or a mud dauber nest in the vent. Again though, it would depend on the vehicle’s year, make, and model.
If your OBD-II scanner reads a P0446 trouble code is present, you could be looking at malfunctioning parts like the purge valve or vapor canister vent valve. But whatever the problem is, you can rest assured that CarParts.com has the right parts to fix your ride.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.
View Comments
That first video was great. That guy did such an awesome narrative. Exactly what I was looking for, exactly what I needed. Thanks!
Hi Chris,
Wells makes some great technical videos! So glad that you found the contents of this article to be helpful!
I have a 09 Suzuki SX4 with 164K miles. Had a P0420, and original O2 sensors. After trying easier fixes, I replaced the O2 sensors. P0420 went away, but now I have P0134, P0138 and P2237. They both look like they are plugged in properly, so what do I do now?
Hello,
If you didn't have those codes beforehand, something likely went wrong when replacing the O2 sensors. Is it possible that you installed incorrect sensors or the sensors somehow got swapped? Also, I should point out that, once you have the O2 sensor issue figured out, there's a good chance code P0420 will return.
I purchased the O2 sensors on Amazon, and they said they were an exact fit for my car. The plugs were such that they couldn't be switched. The only other thing I can think of is that perhaps they were poor quality. They weren't OEM.
https://www.amazon.com/gp/product/B08312NZPL/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
I have a 2006 Chevy Silverado 5.3. I have the code reading error PO 446. EVAP vent silanoid. I've purchased one to replace it. But I can't seem to find it. I've checked under the truck by the gas tank checked lines. Checked on Top of gas tank I'm obviously over looked it. Any ideas where else it should be?
Hello William,
The vent valve is located near the charcoal canister at the fuel tank. This video will show you the location: https://www.youtube.com/watch?v=MFh9fCLzNbw&t=50s
Where is the vent valve on 2002 monte carlo ss?
Hello,
The vent valve is located at the left rear of the vehicle. You can watch this video to get a better idea of the location: https://www.youtube.com/watch?v=AmRKi3NcEJA
Where is the vent valve on a 2004 Chevrolet express 1500
Hi Jose,
The vent valve is mounted to the EVAP canister, which is located on the lefthand side of the frame.
Mud dauber nest in my '07 Tahoe today! Failed smog, check engine light, you called it.