P0446 - Evaporative Emission Control System Vent Control Circuit Malfunction

You want your car to run its best, which is why it’s so troubling when the Check Engine Light comes on. If you notice the P0446 code, you want to know how to fix it right away.

To get you started, I define the P0446 trouble code’s meaning and show you what symptoms it causes. I also review the reasons why this code sets and give you a few tips that might correct it.

Code P0446 Definition

P0446 – Evaporative Emission Control System Vent Control Circuit Malfunction

What Does the P0446 Code Mean?

Trouble code P0446 stands for an Evaporative Emission Control System (EVAP) Vent Control Circuit Malfunction. This code means that the car’s computer detected trouble with the EVAP system vent valve’s function. This vent valve is also known as the purge valve.

The computer is responsible for monitoring and controlling the purge valve. If the P0446 DTC sets, it could indicate that there’s an electrical failure in the circuit or a mechanical problem with the vent valve.

However, this generic trouble code seems to be more prevalent with older model vehicles. While it’s still listed with some newer domestic models, other companies, such as Toyota, don’t have it listed in modern trouble codes.

P0446 Trouble Code Symptoms

In the majority of cases, you will only notice a Check Engine Light because of this code. The P0046 DTC doesn’t normally create any type of performance trouble, making it easy for drivers to ignore.

However, it is possible to notice these symptoms with the P0446 trouble code.

Check Engine Light
Fuel odor (not as likely)

Causes of the P0446 Code

Some of the reasons the P0446 code may be set could be simple to troubleshoot. With a few simple diagnostic steps, you can figure out what’s going on, but you should never guess. Otherwise, you won’t know what’s wrong and you could waste money throwing parts at the problem.

Here are some of the most common faults found through diagnosis.

Malfunctioning EVAP canister vent control valve
Defective electrical connectors or wiring
Loose or broken gas cap
Cracked or damaged fuel tank filler neck
Punctured evaporated system hoses
Failed fuel tank sending unit seal or gasket
Bad carbon canister

How Serious is the P0446 Code?

Low – There’s no pressing reason for you to hurry and fix the P0446 trouble code. The car should continue running as normal in many cases.

However, you should still prioritize getting your car repaired. Many problems are easy to fix, and if something major is wrong, it could lead to bigger problems down the line. Additionally, the car might not be able to pass an emissions test, which would put you in a troublesome situation.

What Repairs Can Fix the P0446 Code?

After your diagnosis, you should know exactly what the cause of the P0446 trouble code is. You will be able to perform the proper repair and get rid of the Check Engine Light.

Here are some of the most common fixes.

Replace EVAP canister vent control valve
Repair electrical connectors or wiring
Repair fuel tank filler neck
Tighten or replace the gas cap
Replace evaporated system hoses
Replace fuel tank sending unit seal or gasket
Replace carbon canister

Common P0446 Diagnosis Mistakes

While the P0446 code is most often triggered by an electrical issue with the purge control valve, the very first step should be to check the gas cap. This is the simplest fix, and it can save you a lot of money.

It’s likely that you refilled the fuel tank and forgot to tighten the cap. If so, you might not need to spend anything to repair this DTC.

How to Diagnose the P0446 Trouble Code

You can troubleshoot this trouble code the same way a mechanic would. Many of the steps don’t require special expertise or tools.

Here are some guidelines you might choose to follow.

Check engine codes to see what else is present. Multiple codes can help you determine the problem with more clarity.
Inspect the EVAP vent control valve. Remove it from your car. It’s typically connected to the charcoal canister. Blow through the openings. If you can’t get air through, the valve is stuck and you need to replace it. Supply ground and power to the solenoid through the steps laid out in your service manual. You should hear the valve click. If you can blow through the valve with it powered, you must replace it.
Inspect the wiring and connectors. If anything looks worn or damaged, replace it.
Inspect the gas cap. If it’s loose, tighten it. If you notice any cracks or damage, replace the cap.
Check for leaks in the EVAP system. Pinch the vent tube to the valve and pressure the system with a smoke machine. If there’s smoke coming from any of the seals or hoses, you need to replace these.

Beyond this, it’s best to have your mechanic take a look at the system. Special equipment and advanced knowledge will be needed to diagnose the system further.

Estimated P0446 Repair Cost

Depending on what you find through the diagnostic steps, you could face a cheap or expensive repair. Our possible repairs are outlined below with approximate labor and parts costs.