Possible causes
– Plugged vapor canister
– Faulty vent solenoid
– Pinched or blocked EVAP hose
– Faulty FTP sensor
– Faulty vent solenoid
– Pinched or blocked EVAP hose
– Faulty FTP sensor
Tech notes
Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.
There is a bulletin for the following models:
1999-2007 GMC Sierra (Classic) Models
2007-2008 GMC Sierra Models
GMC Factory Service Bulletin OBDII Code P0446
When is the code detected?
The Powertrain Control Module (PCM) sets the P0446 code if the vacuum decay rate is greater than a predetermined value.
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Possible a noticeable fuel odor caused by the release of fuel vapors
– Possible a noticeable fuel odor caused by the release of fuel vapors
P0446 GMC Description
The Powertrain Control Module (PCM) monitors the performance of the Evaporative Emission (EVAP) system by applying a predetermined level of vacuum to the EVAP system then monitors the vacuum decay rate.
GMC Technical Service Bulletins for P0446 code
2003 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:ENGINE
2003 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL
2003 GMC SIERRA CLASSIC FUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLY:FILLER PIPE AND CAP
2004 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:ENGINE
2004 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL
2004 GMC SIERRA CLASSIC FUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLY:FILLER PIPE AND CAP
2005 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:ENGINE
2005 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL
2005 GMC SIERRA CLASSIC FUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLY:FILLER PIPE AND CAP
2006 GMC SIERRA CLASSIC ENGINE AND ENGINE COOLING:ENGINE