Pontiac Firebird P0446: EVAP Vent Control Circuit → Malfunction

This is one of the most commonly encountered trouble codes for the Pontiac Firebird Is the Code P0446. The trouble code refers to a number you receive when your Firebird is plugged into an OBDII scanner. It indicates that an error has occurred in the evaporative emission controller system. This code is often found with P0440, P0441 or P0440.

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. This is usually accompanied by P0442. A common problem code is P0420.

Pontiac Firebird 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. You may notice a gas smell after using P0446. Because it is related to the fuel vapor system, P0446 may also cause a slight gas smell.

Pontiac Firebird P0446 Meaning

P0446 stands for a universal OBDII Trouble Code. It means that no matter what make or model vehicle you have, this code will still mean the exact same thing. 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.

Firebird P0446 Trouble code Causes

You can have the P0446 error code trigger on your Pontiac Firebird for many reasons. The most frequent problems that can 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. There are some clips you will need to look for and then remove.
• EVAP 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. It should have a tear or a hole.
• 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. 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. It is possible for this gasket to dry, particularly if vehicles spend a lot of time in dry environments. When it dries out, the fuel tank can’t hold pressure anymore.

P0446 Diagnose- Pontiac Firebird

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Pontiac Firebird P0446. The most commonly used methods to diagnose this code are:

• The mechanic will usually check for any additional trouble 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.
• The mechanic will normally determine what trouble codes are associated with P0446. Check out 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.
• Monitor and check the pressure in your fuel tank.
• 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 most popular Firebird P0446 solutions:

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

You should start with the gas caps and move on to the fuel tanks. This is because the gas caps are the easiest to replace and the least costly.

Here’s a great video on How to check your gas cap.

It's a good idea to try and figure out why your Pontiac Firebird is throwing the P0446 code. This should help. Please leave us a comment below if you have any suggestions. Enjoy your day.