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Engine Codes: P0446 & P1674 - Car Shutdown


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Hi everyone. I need help in figuring out the cause of the car shutting down after reaching normal operating temp. The car is a 2000 996 with E-Gas and it is coming up with codes P0446 - Shutoff valve activated-charcoal filter (function) and P1674 - Final stage engine compartment purge fan. I have read a lot on past posts regarding P0446 and the charcoal canister but I do not believe I have read an occation when the engine actually cuts out. After shutting down, the car would not start again until the following day, or after numerous hours have passed. Does anyone know if the charcoal canister just need to be replaced or is something else involved for the car to shut down. Also, where is the shutoff valve located? Thanks.

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P0446 EVAP Canister Shutoff Valve (Function) – Below Limit

Fault area

– Purge air line blocked

– Flow resistance of EVAP canister too high

The EVAP canister purge valve is very sensitive to contamination. If the lines to the EVAP canister have to be detached, the outside of the canister must be cleaned beforehand.

Check purge air line for blockage. Replace the purge if blocked.

Otherwise you need a new EVAP canister.

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Well i checked the 2 lines in the engine bay and neither seems blocked. I started the engine again and ran the durametric and no codes showed, but the car still shutoff as usual. I guess I'll have to locate the charcoal canister. Im assuming the canister and shutoff valve are located under the car next to the tank?

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Well i checked the 2 lines in the engine bay and neither seems blocked. I started the engine again and ran the durametric and no codes showed, but the car still shutoff as usual. I guess I'll have to locate the charcoal canister. Im assuming the canister and shutoff valve are located under the car next to the tank?

I think one of the actual values in durametic is a reading about how saturated the charcola filter is - you might want to take a look at that value.

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Well i checked the 2 lines in the engine bay and neither seems blocked. I started the engine again and ran the durametric and no codes showed, but the car still shutoff as usual. I guess I'll have to locate the charcoal canister. Im assuming the canister and shutoff valve are located under the car next to the tank?

I think one of the actual values in durametic is a reading about how saturated the charcola filter is - you might want to take a look at that value.

I think I know which one you are referring to, and the reading is -6.

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Well i checked the 2 lines in the engine bay and neither seems blocked. I started the engine again and ran the durametric and no codes showed, but the car still shutoff as usual. I guess I'll have to locate the charcoal canister. Im assuming the canister and shutoff valve are located under the car next to the tank?

I think one of the actual values in durametic is a reading about how saturated the charcola filter is - you might want to take a look at that value.

I think I know which one you are referring to, and the reading is -6.

carbon canister, right? I think it is supposed to be somewhere between 0 and 30, with 30 being full. -6? that's weird

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Well i checked the 2 lines in the engine bay and neither seems blocked. I started the engine again and ran the durametric and no codes showed, but the car still shutoff as usual. I guess I'll have to locate the charcoal canister. Im assuming the canister and shutoff valve are located under the car next to the tank?

I think one of the actual values in durametic is a reading about how saturated the charcola filter is - you might want to take a look at that value.

I think I know which one you are referring to, and the reading is -6.

carbon canister, right? I think it is supposed to be somewhere between 0 and 30, with 30 being full. -6? that's weird

More from 7.8 diagnostics

Possible fault cause

♦ Purge air line blocked

♦ EVAP canister purge valve sticks in the opened position (this

causes continuous vacuum to go from the intake manifold to the

tank system)

♦ EVAP canister shutoff valve is blocked/sticks in the opened position

♦ Flow resistance of EVAP canister too high (filter deformed/

blocked)

♦ Pressure sensor connected incorrectly (polarity reversal)

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  • 3 weeks later...

Time for an update. I replaced the carbon canister with a new one and the car still shuts off so we can eliminate that as the problem. Next thing is the shutoff valve. I located the carbon canister vent valve housing which houses the both the carbon control valve and the shutoff valve. If the shutoff valve is at fault, would I be able to test it by simply disconnecting the shutoff valve and the car will start again? When the car shuts off, I no longer get the fault code with Durametric.

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  • 2 weeks later...

I spoke to a tech and advised me that whatever is causing the car to shutoff after warm up is not related to emission components such as the charcoal canister. He mentioned that it is definitely heat related and that the car is not able to restart until the components affected completely cools down. Anyone?

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I spoke to a tech and advised me that whatever is causing the car to shutoff after warm up is not related to emission components such as the charcoal canister. He mentioned that it is definitely heat related and that the car is not able to restart until the components affected completely cools down. Anyone?

I wonder about fuel pump, or fuel pump relay - I had a failing fuel pump - it starting cutting out when hot under certain circumstances - eventually it would not start until the pump cooled down.

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  • 7 months later...

Time for an update. I replaced the carbon canister with a new one and the car still shuts off so we can eliminate that as the problem. Next thing is the shutoff valve. I located the carbon canister vent valve housing which houses the both the carbon control valve and the shutoff valve. If the shutoff valve is at fault, would I be able to test it by simply disconnecting the shutoff valve and the car will start again? When the car shuts off, I no longer get the fault code with Durametric.

so, did it fix the code P0446? I called EBS racing today and I was told that they get a lot of order placed for a carbon canister and the shut off valve. Which I am guessing that this is the main culprit for the code P0446. I placed an order today because my check engine light came on and gave me the code P0446. There has been a lot of post here but they just tell you what it is and doesn't give you information on how to fix the problem. I have the manual, what I need to know is how to fix it since I already know where it is located and what the P0446 means. So, I will give an update here once I get mine replaced. Hope I get it this week and I hope this fixes the issue.

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  • 2 weeks later...

ok, just need to give you guys an update..I just replaced the shut-off valve and drove the car for about 100 miles...I get no check engine light!!!clapping.gif I'll be driving it tomorrow for another 50 to 80 miles just to make sure..but if you're getting the code P0446, then it is most likely your shut off valve..I bought mine from EBS racing.com for $88.00. I also bought the EVAP canister but didn't use it so I will be returning it. The EVAP from EBS cost me $355.00. I got a quote from my local porsche dealership and they want $472.00 for it..not including tax...so if you need a cheaper OEM porsche parts, EBS racing is one of the place to get it from...

Replacing the shut off valve is an easy DIY! It is connected to your EVAP canister. The EVAP canister is located on the front passenger side. You will need to remove your front right wheel...then the cover(splash guard..or fender well..forgot what's it called..then you will see you canister...remove all the tubing connected to it and pull out your canister..you will see one screww that's holding the shut off valve..once the screw is removed, you just pull out the old one and replace it with your new shut off valve...that's it...

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