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2002 Prizm Dtc Code P0446 Any Common Problems?


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#1 BassPlayer

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Posted 01 April 2006 - 03:05 PM

Hello All,
I have a 2002 Prizm with 44k miles. CEL came on earlier this week. I went to advance auto and got the DTC code P0446. The printout says EVAP Emmision Control System Vent Circuit malfunction.
I did check the gas cap and I think it s fine. I filled the gas tank. no change.
Is there any common failures that cause this error on these models you folks can point me towards?
BTW: I really like the car. Had it since about 30k miles and not one issue.
Thanks.

Want to add I have a Haynes repair manual for corolla/Prizm 93-2002. That says the P0446 code means- EVAP canister vent control valve circuit fault.

#2 Bikeman982

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Posted 01 April 2006 - 05:42 PM

What does the manual say about your emission system? How did you verify that the gas cap was good - did you have it pressure checked?. I would start there and look at the obvious first - the fuses and any component that would set that CEL to come on. Check the wiring schematics and locate that circuit with the canister vent control valve on it. I am sure your manual has procedures for checking components for proper voltage/current requirements. I don't have a 2002 so I am not positive what your corrective action would be, but you can always ask a knowledgable repair technician for some advice. I would ask around before talking to any dealer whose only answer is "Bring it in and we will take a look at it". It may be something minor that you can repair yourself. I would think that because it is in the emission system that the worst effect would be that it would have trouble with passing an emissions test (if your state has one). Other than that, your car should run as before.

Edited by Bikeman982, 01 April 2006 - 05:44 PM.

#3 fishexpo101

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Posted 01 April 2006 - 07:21 PM

The EVAP codes are pretty common for the 8th generation Corolla/Prism clone. Most are more of an emissions nuisance than drivability problem. P0446 is usually tied to not tightening the gas cap until it clicks a few times or a bad gas cap gasket (not holding pressure). Could also be related to any of the vents/valves on the tank itself (Cut off valve, Fill check valve, fuel vent line, etc.)

I got the exact same code on my car after almost 44K-48K miles (don't remember ) - but was a P0446 code. Ran a couple of tanks of gas to eliminated bad gasoline as a possibility, never topped off the tank, etc. When the fuel economy dropped to the low 20s - I knew I had a problem. Turned out to be a cut-off valve at the top of the tank (dealer wanted $300+ for valve and possibily another $360-$450 for the charcoal canister - refused to fix under OEM warranty or Gold extended warranty that I also purchased - fixed it myself for about $30.)

I'd have the code reset and see if it comes back - if it does, then you need to do some diagnostic work to narrow down the problem. Might be worth the $85-$90 that the dealer charges for diagnostics - as it is a lot of work (assuming the dealer is straight - code itself will not point to the problem, they have to spend atleast two hours testing the system, pressurizing, connecting/disconnecting various hoses, probing valves, etc.

#4 ouroboros

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Posted 01 April 2006 - 07:39 PM

The EVAP codes are pretty common for the 8th generation Corolla/Prism clone. Most are more of an emissions nuisance than drivability problem. P0446 is usually tied to not tightening the gas cap until it clicks a few times or a bad gas cap gasket (not holding pressure). Could also be related to any of the vents/valves on the tank itself (Cut off valve, Fill check valve, fuel vent line, etc.)

I got the exact same code on my car after almost 44K-48K miles (don't remember ) - but was a P0446 code. Ran a couple of tanks of gas to eliminated bad gasoline as a possibility, never topped off the tank, etc. When the fuel economy dropped to the low 20s - I knew I had a problem. Turned out to be a cut-off valve at the top of the tank (dealer wanted $300+ for valve and possibily another $360-$450 for the charcoal canister - refused to fix under OEM warranty or Gold extended warranty that I also purchased - fixed it myself for about $30.)

I'd have the code reset and see if it comes back - if it does, then you need to do some diagnostic work to narrow down the problem. Might be worth the $85-$90 that the dealer charges for diagnostics - as it is a lot of work (assuming the dealer is straight - code itself will not point to the problem, they have to spend atleast two hours testing the system, pressurizing, connecting/disconnecting various hoses, probing valves, etc.


I've got a 01 Rolla which should have the same electrical schematic as your 02 (same body style). I can tell you with a great deal of confidence that its probably NOT a fuse that's shorted out. There are several fuses on the instrument panel box that could be related to the EVAP circuit but they are all tied into other vital functions. Your car would most likely be dead if one blew. fishexpo's got it right. Track your mileage... if there's a sudden drop then run through the diagnoses of the valves. If you don't see a drop in mileage the last (and most annoying) possibility would be a ground fault between that sensor and the ECM. That's how I found out about my PO1349 code being the "real McCoy" instead of the ECM crying wolf.

Good luck,

#5 BassPlayer

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Posted 01 April 2006 - 09:04 PM

I only visually looked at the gas cap. To see if the gasketr was in palce and looked ok. I did for the heck of it ask at advance if they had them. yes. $7. Would it be cheaper to buy a new one than get it tested? I a mguessing a dealer would have to test the gas cap?
The Haynes manual does not say too much on the emission system. It shows where the cannister is under the car and where the valve is.

#6 fishexpo101

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Posted 01 April 2006 - 10:09 PM

Yup - dealer will have to pressure test the gas filter as part of the diagnostic. Only the factory service manual will tell you what to check for exactly and the equipment needed - when I did mine, the testing procedure was spread over two section with about 15 pages of material spread between them - lots of testing.

#7 Bikeman982

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Posted 02 April 2006 - 01:33 AM

I only visually looked at the gas cap. To see if the gasketr was in palce and looked ok. I did for the heck of it ask at advance if they had them. yes. $7. Would it be cheaper to buy a new one than get it tested? I a mguessing a dealer would have to test the gas cap?
The Haynes manual does not say too much on the emission system. It shows where the cannister is under the car and where the valve is.


If you can afford the $7 for a new gas cap, you could start there. There are smog test stations in California that always test the cap when they do my emissions testing. Maybe they can do one for you (or a local repair station that has the capability). If it is bad - get a new cap, put it on, have the code reset and see if it comes back. If that does not fix it, you can go for the more expensive parts, or get it diagnosed.

Edited by Bikeman982, 02 April 2006 - 01:33 AM.

#8 BassPlayer

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Posted 02 April 2006 - 09:56 AM

Thanks for the suggestions. I am in NY state. I will try to post updates for others

#9 BassPlayer

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Posted 05 April 2006 - 09:29 AM

Here is an update. NOt sure if related but very well might be. The heater/AC fan is not working except on its hightest ( Hi) setting. I have checked all the fuses according to the manual, both in the car behind the storage comaprtment and the three fuse boxes under the hood.
Its possible I missed one.
Any suggestions?

#10 eabernal

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Posted 08 July 2007 - 11:52 AM

Here is an update. NOt sure if related but very well might be. The heater/AC fan is not working except on its hightest ( Hi) setting. I have checked all the fuses according to the manual, both in the car behind the storage comaprtment and the three fuse boxes under the hood.
Its possible I missed one.
Any suggestions?


I've had exactly the same problem with the fan for 3 months with my 02 Prizm which is basically the same car as yours. But my check engine light only came on yesterday, with the same code as yours: P0446. Did you ever get your problem fixed? Any help would be appreciated!

#11 Nakrah

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Posted 09 May 2008 - 03:51 PM

Here is an update. NOt sure if related but very well might be. The heater/AC fan is not working except on its hightest ( Hi) setting. I have checked all the fuses according to the manual, both in the car behind the storage comaprtment and the three fuse boxes under the hood.
Its possible I missed one.
Any suggestions?


I've had exactly the same problem with the fan for 3 months with my 02 Prizm which is basically the same car as yours. But my check engine light only came on yesterday, with the same code as yours: P0446. Did you ever get your problem fixed? Any help would be appreciated!



I also have the P0441/446 code problem. The AC/Heat fan is unrelated. There is a resistor behind the glove box that needs to be replaced. I purchased mine from a Chevy Dealer for $40. The one they gave me to replace it is MUCH nicer. The old one had bare traces on the circuit board. These corroded and ruined the switch.

High Works because it is a Direct 12V - Fan connection, the others have to be stepped down, where the resistor enters the equation. Working in a Toyota dealership I saw many of these, especially on Camry's where they were mounted under the passenger carpet. WNY = Salty wet winters.