Lexus IS 300 P0446: EVAP Vent Control Circuit → Malfunction

The most frequent trouble code with the Lexus IS 300 Is the Code P0446. The trouble code refers to a number you receive when your IS 300 is plugged into an OBDII scanner. It indicates that an error has occurred in the evaporative emission controller system. You may see it along with the following codes: P0420; P0441; or P0440.

P0446: Evaporative Emission Control System → Vent Control Circuit → Malfunction

The P0446 problem is not usually a serious threat to your car's driveability. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though. It's often associated with P0442. Another common code for trouble is P0420. It often comes with P0446.

Lexus IS 300 OBDII Code Signs

The P0446 code is usually not accompanied with any obvious symptoms. Although the service engine light may come on soon, that's usually all. A slight drop in fuel economy is not uncommon. You may notice a gas smell after using P0446. It is related to fuel vapors.

Lexus IS 300 Meaning P0446

The universal OBDII code P0446 can be used to diagnose trouble codes. It means that no matter what make or model vehicle you have, this code will be the same (IS 300). 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 to ignite the normal combustion process. The EVAP control control circuit will not respond to an ECU if it detects a problem with the vent control circuit. This will cause the engine's service light to illuminate and throw the OBDII P0446 code.

IS 300 P0446 Troublecode Causes

P0446 can trigger the Lexus IS 300 trouble code. The most frequent problems that trigger this 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. There are some clips you will need to look for and then remove.
• EVAP System Hose– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. This can lead to the code P0446. You should look for a hole or a tear in the fabric.
• The Faulty Charcoal Caister– 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. It may be worth your time to get that message and a P0446 to check if the fuel cap is working.
• 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 Diagnosis- Lexus IS 300

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Lexus IS 300 P0446. These are some of the common diagnostics that can be done for the code.

• The mechanic will check for other codes. A mechanic will usually check for additional trouble codes to help diagnose the problem. 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. It includes the purge valve and line as well as the canister.
• 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.
• Monitoring and checking the fuel tank pressure is a must.
• Following the inspections and repairs, the mechanic will conduct two more 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 more common IS 300 P0446 fix:

• Replacement of 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 check your gas cap.

It's your task to determine the cause of Lexus IS 300 throwing the code P0446. We trust this helped. Please leave us a comment below if you have any suggestions. You have a wonderful day.