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P0446

churchy1313

By churchy1313
in Troubleshooting & Recalls

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churchy1313 Enthusiast

churchy1313

Posted
Posted

My trucks check engine light came on Saturday and the code was the P0446.  I check the cap and it was tight.

I drove it Saturday and Sunday with the light on.

This morning after driving about 25 miles the light went out.

 

Any ideas why it came on?

We've had a lot of snow and rain lately, could that cause any issue?

SS502 Senior Enthusiast

SS502

Posted
Posted (edited)
25 minutes ago, churchy1313 said:

My trucks check engine light came on Saturday and the code was the P0446.  I check the cap and it was tight.

I drove it Saturday and Sunday with the light on.

This morning after driving about 25 miles the light went out.

 

Any ideas why it came on?

We've had a lot of snow and rain lately, could that cause any issue?

Did you loosen the cap and retighten it even though it was tight when you checked it? If so you probably cleared it...takes a bit to go away...well it did on my 2008 Avalanche, the 2018 doesn't even have a cap. Do you smell gas?

Edited by SS502
churchy1313 Enthusiast

churchy1313

Posted
  • Author
Posted
5 minutes ago, SS502 said:

Did you loosen the cap and retighten it even though it was tight when you checked it? If so you probably cleared it...takes a bit to go away...well it did on my 2008 Avalanche, the 2018 doesn't even have a cap. Do you smell gas?

I didnt loosen it just made sure it was tight.

dont smell gas

SS502 Senior Enthusiast

SS502

Posted
Posted
3 minutes ago, churchy1313 said:

I didnt loosen it just made sure it was tight.

dont smell gas

I assume you are out of warranty so if it were mine, I'd see if it comes back. Since you didn't do anything other than drive , it probably will come back. There are several things that can kick that code, loose cap, leaky tank, bad evap line, charcoal canister. Hard to say but since you're not smelling gas I doubt you have a leaky tank.

churchy1313 Enthusiast

churchy1313

Posted
  • Author
Posted

I am out of warranty. Its a 2014 with 87,000 miles on it.

I did smell gas about a month ago.  I thought that was because of topped it off and got it too full.

I haven't smelled it since

I  have a few of the common failure parts coming. not going to mess with it until it happens again.

tbarn Senior Enthusiast

tbarn

Posted
Posted

P0446 will not be the result of a loose gas cap or any other leak in the evap system. It is caused by a blockage. Inability to drain vacuum while running it's test.

 

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to be developed in the EVAP system. The engine control module (ECM) commands the EVAP purge solenoid valve Open and the EVAP vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the ECM commands the EVAP purge solenoid valve Closed and the EVAP vent solenoid valve Open. The ECM monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 in H2O in a calibrated time, this DTC sets.

  • Thanks 1
SS502 Senior Enthusiast

SS502

Posted
Posted
14 minutes ago, tbarn said:

P0446 will not be the result of a loose gas cap or any other leak in the evap system. It is caused by a blockage. Inability to drain vacuum while running it's test.

 

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to be developed in the EVAP system. The engine control module (ECM) commands the EVAP purge solenoid valve Open and the EVAP vent solenoid valve Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the ECM commands the EVAP purge solenoid valve Closed and the EVAP vent solenoid valve Open. The ECM monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 in H2O in a calibrated time, this DTC sets.

Thanks for the information, I am never too old to learn! My suggestions were from memory and the old noodle has been updated LOL.

tbarn Senior Enthusiast

tbarn

Posted
Posted
10 hours ago, SS502 said:

Thanks for the information, I am never too old to learn! My suggestions were from memory and the old noodle has been updated LOL.

No problem. There is a TREMENDOUS amount of wrong info or at least wrong assumptions on this forum concerning EVAP codes. I have to chuckle to myself every time I see someone replace a canister for a EVAP code. It can happen but in 36 years at the dealer I replaced very few ( on GM vehicles ). Usually for physical damage.

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  • 4 years later...
DarrenGandhi New Member

DarrenGandhi

Posted
Posted
On 12/17/2018 at 11:35 PM, tbarn said:

No problem. There is a TREMENDOUS amount of wrong info or at least wrong assumptions on this forum concerning EVAP codes. I have to chuckle to myself every time I see someone replace a canister for a EVAP code. It can happen but in 36 years at the dealer I replaced very few ( on GM vehicles ). Usually for physical damage.

What is the fix if not the canister for the EVAP code P0446. i have a 2017 GMC Sierra 1500. 

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