The previous answer was good for high dust environments (and if you have a Ford Van all environments are to be treated as high dust) but for those of us in high corrosion environments, consider the following:
If you have an Explorer (Or Ranger/Mazda B-series) check for a broken wire near the left side framerail near the rear axle.
If you have a Hyundai (including Kia), Nissan (including Infinity) or Toyota (including Lexus or Scion) you should disconnect the electrical connector and then apply and remove 12V power to the vent solenoid/valve. The difference between 12V applied and not applied should be the difference between not being able to blow through it and being able to. After testing at least 5 times, if it fails even once, replace the solenoid/valve.
In the case of Nissan or Toyota, if replacing solenoid/valve it is usually best to replace the canister as well as you might inadvertently break the canister while replacing the solenoid/valve. With many Nissan vehicles, it is almost impossible to not break the canister without using techniques involving unreasonably high fire hazard.
Hey Brian==It is probably the gas cap not on tight. Have the codes removed and see if it comes back on after you tighten the cap.GoodluckJoe
Well, my experience with a 2000 GMC 3/4 ton truck says otherwise.
A loose gas cap will not give you P0446 because that is the code for a failed vent test.
Here's how it works: To check the vent system the engine vacuum valve is opened at the same time as the charcoal filter vent valve is closed. This creates a vacuum in the gas tank and when the vacuum reaches a certain level, the vacuum valve closes and the vent valve opens and a timer is started. If there is a restriction in the vent valve or it doesn't operate electrically, the tank fails to re-pressurize within the correct time and you get a P0446.
Here's what I did: I removed the vent valve and found it choked with a fine dust. I cleaned the valve, but noticed that there was lots of dust in the tube running down to the charcoal cannister and realized the gravel filter in the vent valve is useless at stopping dust. I took out the cannister and discovered an amazingamount of dust clogging it up. I cleaned the cannister by holding it vent side down and sharply tapping it many, many times it while blowing air (at low pressure) through it toward the vent side until it passed air freely both ways. Did I mention that there was an amazing amount of dust that came out of the cannister? I would think that gasoline residues from overfilling might clog up the cannister too, but that didn't happen in my case.
Below are what I consider the possible causes of P0446 in the order of least likelihood (IMO) for a vehicle used in a high dust environment:
Electrical vent driver circuit in computer burned out (especially if the vent valve is shorted), electrical vacuum valve driver circuit burnt out, vent valve coil open or shorted, vacuum valve coil open or shorted, bad vacuum sensor in the gas tank, vent valve filter clogged with dust, charcoal cannister clogged with dust or residues.
Removing and replacing the vent valve and especially the charcoal cannister in a GMC truck is a major, major pain in the a-- because the entire vehicle was carefully engineered by GMC so as to make replacement as difficult as possible. It does no good cleaning and replacing a clogged vent valve as the cannister will be clogged too. A new cannister is about $175, but a cleaned one is free.
BTW, my vent test works perfectly now. Added by Protoart: If you have the P0446 code and the vent valve is bad, don't continue to drive, or you will clog (saturate) the canister with gas for sure. My wife's 05 Scion, check engine light w/ P0441,0442, and 0446.......cleared with my scanner, never came back after I tightened the gas cap
Evaporative emission system purge control valve circuit
P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
usually this means the gas cap is not on tight or is leaking
I t means you have something wrong with your emissions. Check the hose that goes from the Evap Valve (usually a round plastic valve) to Throttle body. Maybe is too soft and when there is a vacuum it clogges.
AnswerP0442 evaporative emissions control system leak detected see "What are OBDII codes and their meanings?"you can also go to www.obd-codes.com for a list of several codes on different models hope this helps- steph
Large evaporative emissions vapor leak. Check gas cap and all hoses from the engine to the gas tank.
Evaporative Emission System High Purge Flow. Relates to your vehicles OBDII compliant system for monitoring vehicle emissions.
P0440 OBDII code is for evaporative emissions control system failure.. check your gas cap though, many times a loose gas cap is the culprit with this code, hope this helps some1 out.
Check every rubber hose from the engine to the fuel tank.
Trouble code P0445 means:Evaporative emission control systempurge control valve circuit shorted
There is air escaping from the gas tank. Often a problem with the gas cap, try tightening the cap, reset the code and see if it comes back on. Essentially it is testing for cracks in the tank.
what does P0466 code EVAP Emission Control System Vent Circuit Malf. mean for a 1996 infiniti i30 Vehicle?
The 0400 - 04## are all emissions related, can be caused by something as trivial as an improperly tightened gas cap or as complex as the EVAPORATIVE EMISSIONS CONTROL SYSTEM, which has a series of hoses, purge valve and charcoal vapor canister filter controlled by the computer. Older cars normally develop leaks in the hoses that can be determined using specialized leak detection testing, normally not for diy level of repair. Most of the 0400 series codes will not affect drive-ability but should be treated ASAP
P0446 Evaporative Emission Control System Vent Control Circuit. The most common cause is the gas cap left off and someone drove the car or the cap was not fully locked it will set the code. Some other causes are leaking evaporative emission plumbing from the fuel tank to the engine compartment, someone changed the fuel pump and did not seal it properly. Failure of a emission component in the evap system. The only way to diagnost these is an OBDII scan tool and a smoke machine the light will come on when the computer does its test of the system and there is a hole as small as .020" 1/20,000 of an inch ! The light can only be turned off by a OBDII scan tool
If it has a circuit malfunction, or is causing a misfire.
This code is defined as: Output Speed Sensor Circuit
Mass or Volume Air Flow Circuit Range/Performance Problem
( P0460 ) - Fuel level sensor circuit malfunction
IAT Sensor 1 Circuit High Input
Trouble code P0043 means: HO2S Heater Control Circuit Low (Bank 1, Sensor 3) Hex code 43 is for a misfire.
In the drivers side footwell, be sure to check the emissions decal though to see if the vehicle is OBD or OBDII certified.
1723 indicates a/t control relay open or short
ummm...if you mean the OBDII it's located on the passenger side foot well. There is a concealed carpeted panel that pops off.
From the OBDII Code book: P0741 - Powertrain: Torque Converter Clutch Circuit Performance/Stuck Off
O2 sensor circuit malfunction, Bank 1 sensor 2. Check the O2 sensor after the catalytic converter.