Engine-Codes - GMC - P0446 GMC

P0446 GMC Code - Evaporative Emission Vent System Performance

- Code Popularity: 82,972 Views
- Repair Importance Level: 1/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0446 GMC?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Plugged vapor canister
  • Pinched or blocked EVAP hose
  • Faulty Evaporative Emission Vent Solenoid Valve
  • Evaporative Emission Vent Solenoid Valve harness is open or shorted
  • Evaporative Emission Vent Solenoid Valve circuit poor electrical connection
  • Faulty Fuel Tank Pressure (FTP) sensor

Code 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





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How to Fix the DTC P0446 GMC?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P0446 GMC code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • A noticeable fuel odor may result from fuel vapor release

What Does the P0446 GMC Code Mean?

This Diagnostic Trouble Code (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.
P0446 GMC Code - Evaporative Emission Vent System Performance

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