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Ron Z.
Ron Z., - Pontiac Tech -
Category: Pontiac
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Experience:  18+yrs experience. State Inspector and Pontiac Diagnostics
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Why is there a p0446 code on my 2001 pontiac grand prix gt?

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why is there a p0446 code on my 2001 pontiac grand prix gt?

The P0446 is pointing to a fault in the EVAP Cansiter Vent Valve. Inspect the vent valve vacuum lines for any disconnections, holes or kinks. Check the electrical connector for any loose or broken wires. If the visual inspection checks ok, suspect a faulty Vent Valve.



  • Raise the vehicle. Refer to Lifting and Jacking the Vehicle.
  • Remove the left inner rear fender.
  • Disconnect the evaporative emission (EVAP) vent valve electrical connector (1).
  • Disconnect the vent hose (4) from the EVAP vent valve.
  • Remove the EVAP vent valve from the bracket (2).
Customer: replied 5 years ago.
along with that theres a P0420 code

The P0420 is in a totally different system, and more than likely, unrelated. The P0420 is most commonly the sign of a failing Catalytic Converter. The oxygen sensors measure the amount of pollutant going into, then out of the converter. When they report to the PCM the values, and these values are below what the PCM is pre-programmed to see, it's determined the convter is losing it's ability to perform it's job correctly, and will need to be replaced.

Customer: replied 5 years ago.
thanks for the info. the worst thing about all these codes is that the EVAP Canister Vent Valve leaks fuel everytime i go to a gas station to fill my car . I am there at the fuel pump pumping gas into my car and at the same time while i am pumping gas that EVAP Canister Vent Valve is leaking fuel

If thats the case- then you now know why you have a P0446 code! You'll need to obtain a new one from a GM Dealer. "Emissions" related parts are not offered in after market parts stores.... yet...


Customer: replied 5 years ago.
I did replace the EVAP canister vent valve with a GM one and its still the same problem.

And there are no broken, disconnected or holed vacuum lines?!


A restricted or blocked Evaporative Emission (EVAP) vent path is detected by the Powertrain Control Module (PCM) monitoring the Fuel Tank Pressure (FTP) during normal operation. The PCM commands the Evaporative Emission (EVAP) vent valve OFF (open), and the EVAP canister purge valve ON (open). The fuel tank pressure should remain low as vacuum is drawn on the EVAP system. If the vent path is blocked or restricted, the vacuum level will increase and DTC P0446 will set.


The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.



Customer: replied 5 years ago.
i never did a visual inspection on the vacuum lines.So the problem is the vacuum lines or the EVAP vent valve electrical connection/electrical problem?

Correct. It's a fairly straight forward code. Most commonly there is a pinched or kinked vacuum line. Also very common is the vent valve itself cracks. Definitely re-check those vacuum lines.


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