This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
Code P0446 indicates an Evaporative Emission Control System Vent Control Circuit Malfunction
Modern cars have an Evaporative Emission Control System or EVAP, for short. This system traps toxic vapors before they get out and recirculates them inside the engine. OBD2 code P0446 indicates that one of the vent valves within the EVAP isn’t working correctly.
Although this code refers to the vent valve within the EVAP, the problem is seldom the valve itself. Instead, the most common reason for the code to appear is a missing or loose gas cap. Beyond that, here are some other elements that can cause the vent valve to malfunction.
- Faulty EVAP System Hose - These hoses carry emissions to the charcoal canister to get filtered. If the tube isn’t connected properly or damaged, it can cause a problem with the vent valve.
- Leaking Fuel Tank - The EVAP system needs to be pressurized to work correctly. If the fuel tank is leaking, air is getting inside, which can trip up the sensors.
- Broken or Faulty Charcoal Canister - This component is rarely the cause as it doesn’t have many parts that can break down. However, if you’ve checked everything else and the code remains, you might have to replace your canister.
Fortunately, this code isn’t critical, and you won’t notice any performance issues with your car. Beyond the check engine light coming on, you might smell gasoline, or your fuel economy may dip slightly.
If those symptoms are present, then a fuel tank leak is the likely culprit. Otherwise, it’s probably the gas cap or the system hose.
Before inspecting anything or trying to perform any repairs, you should first see if the code reappears. Follow these steps to ensure that you don’t do any unnecessary work.
- Step One: Get freeze frame data from your OBD2 scanner. In some cases, more than one code may be present.
- Step Two: Clear all codes with the scanner.
- Step Three: Drive for a while and see if the check engine light comes back on. If it does, repeat step one. In some instances, additional codes may not be present the second time.
- Step Four: Tighten the gas cap, and look for any damage. Sometimes, the cap itself may be cracked, which can cause problems with the pressure in the EVAP system. Repeat steps one through three to see if the light comes back on.
- Step Five: If the light does return, you will need to do a visual inspection of your EVAP system. Pay close attention to the hoses. If the tube is damaged, cracked, or not secured tightly, then you have to either tighten it or replace it.
- Step Six: Use a scanning tool to check the pressure of your fuel tank. This equipment can tell you if there’s a leak. Also, if you notice a strong gasoline smell, that can indicate a leak as well.
- Step Seven: If all else fails, then you can check your charcoal canister for damage. Again, this component is rarely the culprit.
Once you repair or replace something, be sure to clear the code and do another test drive. Following these steps can prevent you from trying to fix the wrong thing. Not only that, but if you repaired multiple items, you wouldn’t know which component actually cleared the code.
Typically, the mistake is when you assume that one element is broken without running down the list step by step. Because there are so many pieces to your car’s engine, skipping ahead is never wise.
How serious is this?
As we mentioned, you can drive normally with this code present. However, if the cause was a fuel leak, you need to fix that as soon as possible. While it won’t cause irreparable damage to the vehicle, it will affect your fuel mileage and efficiency.
Also, it’s always a good idea to fix any problem that causes a check engine light. If not, it’s impossible to tell when another component malfunctions, since the same light indicates a wide array of problems.
What repairs can fix the code?
The most common way to remove this code is to check and tighten the gas cap. However, if that isn’t the culprit, these repairs should correct the problem.
- Repairing a Leaky Fuel Tank
- Replacing a Broken Gas Cap
- Replacing the EVAP Hose
- Repairing or Replacing Your Charcoal Canister
Typically speaking, any issue with your EVAP system can create a network of problems. In most cases, you’ll see multiple codes, particularly if the cause is a leaky fuel tank or faulty charcoal canister. Again, you want to fix these issues now so that you’re not blindsided by another code you missed because the check engine light was already on.
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