P0446: Evaporative Emission Vent Control Circuit Fault

This error code is caused by an Evaporative (EVAP) Emissions vent control circuit fault. We have compiled an excellent resource for you to find out everything you ever wanted to know about P0446.

Read below to learn more:

What is code P0446?

The EVAP system is an important emissions system on your vehicle. Evaporative emissions are the hydrocarbon vapors that are released into the atmosphere during normal operation.

Fuel sloshing around in the fuel tank, heating up and cooling all contributes to the liquid fuel in the tank converting into a vapor. This vapor if not controlled is released into the atmosphere where it causes harm to our environment.

The vehicle controls these emissions with a series of charcoal canisters, purge valve, vent valve, as well as various sensors.

The vent valve opens/seals access to fresh air to enter the charcoal canister. This code is caused when the PCM detects a fault in the EVAP vent valve circuit. The electrical side of this component.

By monitoring various inputs such as a fuel tank pressure sensor the powertrain control module (PCM) can complete diagnosis of this system to make sure it is functioning properly.

If it detects no functionality of the circuit, it will set code P0446.

Symptoms of P0446

Usually, drivers cannot see the indications of the fault in the vent’s circuit. But, some indications can’t be ignored. The rare but noticeable indications of P0446 are:

  • Check engine light or illuminated malfunction indicator lamp.
  • An unusual odor from the vehicle
  • Other Possible error codes, P0456, P0441, etc.

If you notice any of these symptoms it is always a good idea to scan your vehicle with a scan tool to verify if this code is present or not.

Causes of Code P0446

Some manufacturers have different self-diagnosis methods of checking for this fault code. Because of this the causes of P0446 being set may vary according to the model of the car.

Some of the leading causes of the P0446 are as under:

  • Clogged vent valve or vent hose
  • Leakage in the EVAP system
  • Faulty or damaged wiring/connector
  • Fault in the pressure sensor of the EVAP system
  • Damaged charcoal canister

How to Fix the Code P0446?

Fixing the problem that caused code P0446 is a challenge itself. First, you need to check the specifications, including the vehicle’s model, year, and engine.

Once you have this information you can do some simple checks to diagnose this code.  

There is one simple check that can be done to see if the vent valve is functioning properly. You will need a test light and a bi-directional communication able scan tool.

Remove the wiring connector to the vent valve, place the test light across the two terminals of the connector. (Generally, the vent valve is simple with only a power and ground present to the valve)

When commanding the vent valve open and closed monitor the test light. Does the test light illuminate when commanded on, and when commanded off does the test light turn off.

If the test light illuminates correctly than there is an internal fault in the vent valve assembly and needs replaced.

If it does not light up correctly the wiring to the vent valve will need to be diagnosed and inspected to find the cause of the fault.

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Is It Safe to Drive a Vehicle with P0446?

According to the experts, P0446 won’t get you in much trouble. You can even drive the vehicle with P0446.

However, this code does not generate such life-threatening issues, yet the MIL needs attention whenever it is illuminated. Also, the vehicle will be unable to clear the emission test if the engine is not working correctly.

Costs to Fix P0446

The costs to repair this fault code can vary significantly, just like the problems that caused it.

 The estimated repairing costs for some of the problems caused by P0446 are as under:

  • Vent valve wiring repair $40-$240
  • Damaged EVAP line $100-$300
  • Faulty powertrain control module (PCM)

As always, these values are estimated and may vary according to the model of the vehicle and damage present

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