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. The vent control valve is normally opened when the engine is on, and the purge volume control valve is normally closed and is controlled by the ECM to open when it is ready to purge the stored fuel vapors from the charcoal canister. However, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly when the vehicle is turned off. During the leak test, the ECM closes the vent control valve to create a sealed EVAP system. 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 proper pressure during the active EVAP leak test.

What Are The Symptoms Of P0446?

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

What Is The Cause Of P0446?

  • Missing, defective, damaged, or loose gas cap (most common)
  • Defective EVAP Canister Vent Control Valve
  • 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
  • Open or shorted electrical connections

How Serious is Code P0446? – 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.

Tools Needed to Diagnosis Code P0496

    • FIXD 
    • Digital multimeter
    • EVAP smoke machine leak checker
    • Fused jumper wires
    • Vehicle specific service manual

How To Diagnose And Repair Code P0446:

Difficulty of Diagnosis and Repair – 2 out of 5

 

  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. 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. If your gas cap is loose, tighten it and clear the code. 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 is not always noticeable. If your gas cap was not loose and you do not see any indications of failure, try replacing the gas cap anyway and clearing the codes. Gas caps are relatively inexpensive and are often the fix for code P0446.
  3. If the fuel cap didn’t fix it, perform an EVAP system leak check: Pinch off the vent tube to the EVAP Vent Control Valve. Pressurize the EVAP system with an EVAP smoke machine leak checker. Check to see if you see any smoke leaking out from any hoses or seals. If there are any leaks, repair leaks and check to see if the concern is resolved.
  4. If you find no leaks, check the EVAP vent control valve for proper operation. This valve can get sticky, have debris caught in it, or the internal solenoid can fail and not operate. To test: Remove the EVAP vent control valve from the vehicle. (Tech Tip- The EVAP vent control valve is usually located under the car in the rear of the vehicle by or attached to the charcoal canister.) Verify with no power or ground supplied that you can blow through the valve’s openings. (If you can’t blow through the openings, the valve is stuck closed and needs to be replaced.) Now, supply power and ground to the solenoid (reference the service manual for your vehicle to find out which pins to supply power and ground to) the valve should click and now you shouldn’t be able to blow through the openings. If you can blow through the valve when it is powered on, then the valve is faulty and needs to be replaced.
  5. If at this point the vehicle is still setting the same code, you may have an electrical problem and will need to bring it to a shop to have further diagnostic work performed.  

Estimated Cost of Repair

For error code P0446, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

  • Gas Cap $20-$60
  • EVAP Line $20-$100
  • EVAP Vent Control Valve $150-$200

Was this post helpful?

Comments 27

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!

Paul Benson

May 23, 2019

Can I fix this myself?

Bobby

January 4, 2019

This tool is the greatest thing I ever bought you guys are great

FIXD Marketing

January 6, 2019

Thanks Bobby! We appreciate it!

FIXD Team

Rick

January 7, 2019

How did you figure out this specific problem?

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?

Maria

August 26, 2019

No, coolant reservoir is only used with the radiator

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.

Jimmie

January 7, 2019

What if you are getting the P0446 code and
the Tahoe is hard to start after putting gas in the tank??

Michael McCloskey

February 13, 2019

I have that on my Silverado; they diagnosed it as fuel pump and are replacing the fuel pump today.

Doc

April 3, 2019

On my 2004 Sierra replacing the Purge Valve in the Intake Manifold fixed this same problem.

Danny Mac

April 15, 2019

I was having this problem on my 2008 Chevy Malibu. Replacing the purge valve fixed the problem.

Tim

January 24, 2019

I have a 1998 Chevy Silverado C1500 (5.7L). Getting codes P0446 and P1441 Where does this point to for the fix assuming that maybe one problem is causing both codes?

Rey

July 17, 2019

I had issues with not being able to fill up my tank w/out it clicking off 100 times. 15+ min to fill-up my tank was getting out of hand. So, I looked up this symptom and it suggested the evap canister needs to be replaced. Mind you, no code had ever shown up, but I replaced the darn thing for $600 for the part. Pretty easy swap. Anyhow, I’m still getting the same symptom at the pump; which is quite annoying; and still, no “check engine” light. S.O.S!!! Thoughts?

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