My 1999 Toyota Rav 4 AWD was diagnosed with troubleshooting code P0446 which is defined as an evaporative emission control system vent control circuit fault. Is this an expensive problem to have repaired? How much should it cost a mechanic to fix it?\r\nThe vehicle has 92,000 miles on it.\r\nThank you.

P0440 = Evaporative Emission System.
P0441 = Evaporative Emission System Incorrect Purge Flow.
P0446 = Evaporative Emission System Vent Control Circuit.
The vehicle is fitted with a system that recycles unburnt fuel in the exhaust gases, usually referred to as the EVAP system. This sounds like a possible issue with the valve built into this system.

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction. The code P0446 is set when the engine computer recognizes a fault or restriction at the vent control part of the Evaporative emission control system (EVAP).

https://www.obd-codes.com/p0446

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction The code P0446 is set when the engine computer recognizes a fault or restriction at the vent control part of the Evaporative emission control system (EVAP). The description of the fault varies between different car manufacturers, but one thing is common, the code P0446 doesn't directly point to a defective part; some testing might be required to pinpoint the faulty component. What can cause the code P0446: - faulty vent control valve - blockage at the vent hose, vent filter or vent control valve - open or short in the vent control valve circuit - bad charcoal canister - EVAP system leak - faulty EVAP system pressure sensor - bad vacuum switching valve (VSV) - stuck open purge valve (solenoid)

Error Code: P0440
Fault Location:
Evaporative Emission (EVAP) System - Malfunction
Possible Cause:
Malfunction Indicator Lamp (MIL) active.
Soution:
Check Evaporative Emission (EVAP) System Sealing.
Check Evaporative Emission (EVAP) Canister Purge Regulator Valve .
Check Evaporative Emission (EVAP) Canister Purge Solenoid Valve .

Error Code: P0441
Fault Location:
Evaporative Emission (EVAP) System - Incorrect Flow Detected
Possible Solutions:
Check Evaporative Emission (EVAP) Canister Purge Regulator Valve .
Perform Output Test.
Check Evaporative Emission (EVAP) Canister Purge Solenoid Valve .
Check Evaporative Emission (EVAP) Canister.
Perform Basic Setting.
Check Pipes between Tank Breathing and Throttle Body.

Error Code: P0446
Fault Location:
Evaporative Emission (EVAP) System, Vent Control - Circuit Malfunction
Possible Cause:
Wiring harness.
Evaporative emission (EVAP) canister purge valve.
Engine control module (ECM).

P0446 Evaporative Emission System Vent Control Circuit.
The following are descriptions of all Evaporative possible codes:

P0441 Evaporative Emission System Incorrect Purge Flow
P0442 Evaporative Emission System Leak Detected (small leak)
P0443 Evaporative Emission System Purge Control Valve Circuit
P0444 Evaporative Emission System Purge Control Valve Circuit Open
P0445 Evaporative Emission System Purge Control Valve Circuit Shorted
P0446 Evaporative Emission System Vent Control Circuit
P0447 Evaporative Emission System Vent Control Circuit Open
P0448 Evaporative Emission System Vent Control Circuit Shorted
P0449 Evaporative Emission System Vent Valve/Solenoid Circuit
P0450 Evaporative Emission System Pressure Sensor/Switch
P0451 Evaporative Emission System Pressure Sensor/Switch Range/Performance
P0452 Evaporative Emission System Pressure Sensor/Switch Low
P0453 Evaporative Emission System Pressure Sensor/Switch High
P0454 Evaporative Emission System Pressure Sensor/Switch Intermittent
P0455 Evaporative Emission System Leak Detected (large leak)
P0456 Evaporative Emission System Leak Detected (very small leak)
P0457 Evaporative Emission System Leak Detected (fuel cap loose/off)
P0458 Evaporative Emission System Purge Control Valve Circuit Low
P0459 Evaporative Emission System Purge Control Valve Circuit High
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At least the cap isn't loose for the gas tank.

I would clear the code with an OBD-II Scanner 'erase code' button, and see how long it takes for it to come back.

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction

The evaporative emission control system checks to make sure there are no leaks in the lines that run from the gas tank to the charcoal canister and up to the engine. It also checks to make sure the gas cap is sealing correctly.
It may just be that the cap was not on tight and the code was tripped.

A dusty environment can also clog the vent line and cause this code.
Have the code cleared and see if it comes back. Some auto parts stores like Auto Zone can read and clear the codes for you.
Hope this helps.

where is Evap Emission Control System Purge Flow fault

Error code P0446 is an Evaporative Control System vent control malfunction. DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the certain components, or when there is a malfunction in either the VSV for EVAP, the VSV for
pressure switching valve, or in the vapor pressure sensor itself.

ECT stands for engine coolant temperature. So I would start by making sure that your engine coolant system is not leaking and is full of coolant.If you want to tackle the job yourself you could purchase Haynes techbook # 10206 OBD -2 and electronic engine management systems or check your local library they may have a copy and they have troubleshooting steps you can do with a scan tool or multimeter. Good luck and hopefully this helps you a little.

These codes are all for the Evaporative Emissions System.

P0440- Evaporative emissions system fault- just saying there's something wrong with the system.

P0441- Evaporative emissions system- Incorrect purge flow- saying that the system isn't purging the raw fuel vapors (hydrocarbons- HC) as well as it should.

P0446- Evaporative emissions system- Control valve circuit low- there is a valve, usually located on the charcoal canister at the rear of the vehicle, that opens to allow fresh air to enter the evaporative emissions system as the engine vacuum purges the fuel vapors from the charcoal canister and closes when purge is not needed to prevent leakage of those fuel vapors to the atmosphere (HC is a greenhouse gas and is regulated as such by the fed gov't).

Given that you have the incorrect purge flow code and the control valve code together, my bet is that the vent control valve has failed (causing the P0446) and is not opening to allow fresh air into the system to displace the air from within the system that is being pulled to the engine. Since you have no fresh air entering the system, the engine will pull a vacuum on the system instead of the vapors "flowing" into the engine (causing the P0441).


I hope that this is helpful to you!!!


ASE Master Technician with L1 and X1 Certifications; Nissan Scope Technician; Chrysler Level 3 Silver Technician- 12+ years experience.