P0446 – Meaning, Causes, Symptoms, & Fixes

Code P0446 Definition

Evaporative Emission Control System Vent Control Circuit Malfunction

What Does P0446 Mean?

The evaporative emission control (EVAP) system prevents fuel vapors from escaping into the atmosphere. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister. The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned. The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge valve. Both the vent control valve and the purge valve are usually open when the engine is at normal operating temperature. However, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly. During the leak test, the ECM closes the vent control valve and purge valve to create a vacuum. When P0446 is triggered, the ECM has detected a short in the circuitry to activate the vent control valve, or the EVAP system failed to maintain the vacuum during the active EVAP leakdown test.

P0446 Symptoms

  • Check Engine Light is on
  • Slight decrease in fuel economy
  • Gasoline smell

P0446 Causes

  • Missing fuel cap
  • Defective Evaporative Vent Valve
  • Defective or damaged fuel cap
  • Distorted, damaged or cracked Fuel Tank Filler Neck
  • Torn or punctured Evaporative system hose(s)
  • Defective Fuel Tank Sending Unit gasket or seal
  • Split or damaged Carbon Canister
  • Defective or damaged fuel tank

Code P0446 Severity – Low   

The driver will likely not notice any symptoms associated with P0446 other than the check engine light being on. However, as with all check engine light diagnostic trouble codes, you should repair it as soon as possible to return the vehicle to normal operation.

Code P0446 Diagnosis Steps

How To Diagnose P0446

  1. Scan your vehicle to verify P0446 is the only code present. If other codes are present regarding fuel pressure or the fuel system, repair and diagnose those first.
    1. If it is paired with P0441, P0440, and/or P0446 there is most likely a solenoid failure, leaking charcoal canister, or a more complex EVAP leak.
  2. Inspect your gas cap to see if it is loose or damaged
    1. If your gas cap is loose, tighten it and clear the code.
    2. Inspect your gas cap for physical damage or deterioration. However, it should be noted that damage to the gas cap or deterioration of its components are not always noticeable. If your gas cap was not loose and you do not see any indications of failure, try replacing the gas cap anyways and clearing the codes. Gas caps are relatively inexpensive and are often the fix for code P0446.
  3. Check for cracked or disconnected EVAP hoses near or connected to engine air box
    1. Replace cracked/disconnected hoses
    2. Clear code
  4. Inspect the fuel tank and charcoal canister for damage and leaks. Replace if necessary.
  5. Check both the charcoal canister vent valve and purge valve for proper operation. These valves can get sticky causing leaks or the internal solenoid can fail and not operate. To test:
    1. Disconnect the valve connector and test that the valve is receiving power with a multimeter
      1. If there is no power, there is most likely a wiring problem or a faulty powertrain control module.
      2. Tech Tip- The canister vent valve is usually located under the car in the rear of vehicle by or attached to the charcoal canister. The purge valves are usually under the hood near the airbox or intake manifold.
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Comments 16

Marc Clawson

June 27, 2018

Already took care of it, the pressure/purge sensor on top of the fuel tank wasn’t functioning

FIXD Marketing

June 28, 2018

Good to hear Marc!

Brittni

July 6, 2018

I just got this code on my car is it still safe to drive until I can repair? Will that cause car to cut off?

FIXD Marketing

July 9, 2018

Hello,

The trouble code P0446 will not give you any drivability issues, but just like all check engine lights, it should be repaired as soon as possible.

The FIXD Team

Darrell

July 12, 2018

I’m still getting a P0446 code and haven’t been able to figure out why. I’ve installed a new gas cap, vent solenoid valve. Purge valve and pressure sensor unit on the fuel tank and still get the P0446 code. Any ideas?

FIXD Marketing

July 12, 2018

Hi Darrell,

There are a number of possibilities of this trouble code and it’s awesome to hear that you’ve eliminated a few already! Before moving forward I would advise that you run tests to make sure you need to replace the parts or not. Check out this video on diagnosing and finding your issue!

If you still run into problems you may need to go to a mechanic.

Thank you,
The FIXD Team

Chuck

July 12, 2018

FIXD is such a great thing. Thank you so much. I’ve used it several times for problems on my car and work van. They have been 100% right. Every time. Saved me tons of money. But most of all. Saved me aggravation. Love it !!!

Don

August 16, 2018

I hav a 2006 Chevy 3500 Express RV conversion. My generator runs on fuel from my tank. Everything else checks out. Any ideas?

A Man

August 17, 2018

Took my Buick Century in, they did a smoke test and it was repaired ($400 for parts including a new gas cap), the code came back; the mechanics took a second look and said a purge valve o-ring was stiff and wasn’t sealing, said the cost was $35 to fix that….makes me wonder if the $400 for the evap solenoid and new gas cap was really needed.

Clem Williams

September 1, 2018

Got a po446 code. Put on new gas cap, changed evap, even got cadillac converter checked, code wont clear. 2006 cadillac dts.

Jesus Solis

September 23, 2018

I have a 2008 Ford F-150 4.6liter engine,I replaced the intake manifold because it was leaking and after I replaced the code p0446and p0452 codes came up on the check engine light also it shakes when I’m driving and don’t have the same power.

Johnny coy

October 16, 2018

I took my brothers Chevy silveraldo and had it hooked up to diagnostic and two codes came up. One I pretty much understand with thermostat. But this evaporative emission system vent control circuit has me in a pickle. My question is call I still drive it until I can get it fixed? Thsnks

Patrick

October 20, 2018

I had an issue where I popped a few fuses and relays, I want to double check this particular relay or fuse, but can’t figure out which ones to check.

Andrew

October 28, 2018

Hi
I have P0441,p0442 and P0446 showing on my Lexus RX .
Please should I do.

Regards

Saul Ibarra

November 4, 2018

Could this issue have anything to do with the Coolant Reservoir?

yeskay

November 11, 2018

Lexus ES 300 – got the only code p0446. replaced with a new evap canister assembly . After driving for about 6 months the same code came again. what else would cause this single code.