P0446 OBDII Code: Evaporative Emission Control System Vent Control Circuit Malfunction

A common problem code is Code P0446. The trouble code refers to a number you receive when your car is plugged into an OBDII scanner.  A P0446 code indicates that an issue is occurring in the evaporative exhaust control system.  This code is often found with P0420 or P0441 codes.

P0446:  Evaporative Emission Control System Vent Control Circuit Malfunction

Normally, P0446 does not pose a threat to vehicle driveability.  Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though.

P0446 OBDII Code Symptoms

Most commonly, the P0446 code does not cause any symptoms.  Although the service engine light may come on soon, that's usually all.  A slight drop in fuel economy is not uncommon.  A slight gas smell may be caused by P0446.  Because it is related to the fuel vapors system, P0446 may also cause a slight gas smell.

Definition of P0446

The OBDII universal trouble code is P0446. The code can be used regardless of the make and model of your vehicle. Technically, the code stands for:

Evaporative Emission Control System Vent Control Circuit Malfunction

The EVAP system collects fuel vapor from fuel tanks and then sends it to the intake of the engine in order for them to ignite in normal combustion.  If the EVAP control valve purge valve does not respond to the ECU it will emit the OBDII code P0446.

Trouble code P0446

The ECM can be triggered by many factors, including the P0446 code. The most frequent problems that trigger the code are:

• Vapor Canister Purge Valve– One of the most common causes of the P0446 code is the vapor canister purge valve.
• It’s really easy to replace. You will need to locate and take out a few clips.
• Hose for Evap System– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak.  The P0446 code will be generated.  You should look for a hole or a tear in the fabric.
• A Faulty Canister of Charcoal–  The charcoal canister is often the cause of P0446.
• Fuel Tank Sending Unit– It is possible for the fuel tank sending unit to go bad.  It can cause a disruption in the line pressure, throwing off the code.
• Fuel Cap– A bad fuel cap can cause the code to be thrown for sure. Often, you’ll get a message informing you that the fuel cap is off even when it is on. You may not get the message but a P0446. This will save you time and money.
• Fuel Filler Neck–  There is often a gasket where the fuel filler neck connects with the gas tank.  The gasket may dry out especially if the vehicle is in dry conditions.  When it dries out, the fuel tank can’t hold pressure anymore.

P0446 Diagnostics

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your P0446 code.  These are some of the common diagnostics that can be done for the P0446 code.

• The mechanic will check to make sure there are no other codes.  It is easier to diagnose problems if there are more codes.  That’s because when they appear together in certain combinations, there will often only be only a few conditions that will throw any combination of codes at one time,
• Once the mechanic has determined the trouble codes associated with P0446, he or she will usually Take a look at the EVAP system.  These include the line and purge valve.
• A mechanic will examine the gas cap and verify that it is able to withstand high pressure.  If you are getting a warning that your gas cap is off, even when it’s on, replacing it will more than likely clear this code.
• Monitor and check the pressure in your fuel tank.
• After for the issues above, the mechanic will perform two tests:  A smoke test, and they’ll use a scan tool to confirm that the EVAP solenoids and valves are operating properly.

Most common P0446 fixes

These are some of the most popular P0446 solutions:

• Replacing the gas cap
• Replacing EVAP lines
• Replace charcoal canister
• Change the fuel tank

It is best to begin with the gas cap, and then work your way up to the fuel tanks. The gas cap is the most difficult and cost-effective item to replace.

Here’s a great video on How to test your gas tank.

We wish you all the best in finding out what's causing your vehicle throw the P0446 codes. This information is hoped to be helpful. You can add any additional information by leaving a comment.