GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2007 🢒 G3 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0446

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0446: Evaporative Emissions (EVAP) Vent System Performance

Circuit/System Description

A restricted or blocked evaporative emission (EVAP) vent path is detected by the control module commanding the purge valve ON (open) and the vent valve ON (closed) allowing a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the purge valve OFF (closed) and the vent valve OFF (open) while monitoring the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, DTC P0446 will set.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.

Control Module Command

EVAP Canister Purge Valve

EVAP Canister Vent Valve

ON

Open

Closed

OFF

Closed

Open

Conditions for Running the DTC
    • DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0300, P0402, P0404, P0405, P0406, P0443, P0451, P0452, P0453, P0454, P0461, P0462, P0463, P0464, P0488, P0498, P0499, P0502, P0506, P0507, P2110, P2195, and P2196 are not set.
    • One of the following conditions is met:
       - The ignition is off for greater than 12 hours.
       - OR
       - The start-up intake air temperature (IAT) and the start-up engine coolant temperature (ECT) are within 8°C (46°F).
    • The ignition 1 voltage is between 11-16 volts.
    • The barometric pressure (BARO) is greater than 72 kPa.
    • The start-up ECT and start-up IAT are between 4-34°C (39-93°F).
    • The start-up IAT is 3°C (37°F) less than the actual IAT.
    • The purge enable time is less than predetermined value based on startup ECT.
    • The fuel level is between 6-93 percent.
    • The engine run time is between 1-360 seconds plus purge enable time.
    • The restricted path test time is completed in less than 220 seconds.
    • The DTC run once an ignition cycle when the above conditions are met.

Conditions for Setting the DTC
    • The fuel tank pressure is greater than 8 inches H2O at cold engine startup.
    •  The above condition is present for at least 2 seconds.

Action Taken When the DTC Sets

DTC P0446 is a Type A DTC.

Conditions for Clearing the DTC

DTC P0446 is a Type A DTC.

Diagnostic Aids

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.

Reference Information

Schematic Reference

Evaporative Emissions Hose Routing Diagram

Description and Operation

Evaporative Emission Control System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Special Tools Required

    • J 41413-SPT High Intensity White Light
    • J 41413-VLV EVAP Port Vent Fitting Tool
    • J 41413-200 Evaporative Emissions System Tester (EEST)
    • J 41413-300 EVAP Cap and Plug Kit
    • GE-41415-50 Fuel Tank Cap Adapter

Circuit/System Verification w/Service Bay Test
  1. Verify the EVAP system using the EVAP Service Bay Test. DTC P0446 should not set.
  2. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

Circuit/System Verification w/o Service Bay Test
  1. Ignition ON, observe the DTC information with a scan tool. Verify DTCs P0443, P0452, P0453, P0458, P0459, P0498, or P0499 are not set.
    2. ⇒If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Observe the scan tool fuel tank pressure (FTP) sensor pressure parameter. Verify the FTP sensor pressure parameter is near 0 in H2O.
  3. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing
  1. Ignition OFF, remove the fuel tank filler cap.
  2. Ignition ON, observe the scan tool fuel tank pressure sensor voltage parameter. Verify the FTP sensor voltage parameter is less than 4 volts.
    3. ⇒If greater than 4 volts refer to DTC P0452 or P0453 .
  3. Start the engine. With a scan tool seal the EVAP system using the EVAP purge seal function. Command the purge open to 20 percent. Seal the system at -8.00  in H2O. Exit the system seal. Verify the FTP sensor pressure parameter decreases to 0 in H2O.
    4. ⇒If the scan tool FTP sensor parameter does not decrease, check for a blockage or restrictions in the EVAP vent hose, or replace the EVAP vent solenoid valve.

Repair Instructions

Evaporative Emission Canister Vent Solenoid Valve Replacement

Repair Verification w/Service Bay Test

Verify the EVAP system repair using the EVAP Service Bay Test

Repair Verification w/o Service Bay Test
  1. Start the engine.
  2. With a scan tool seal the EVAP system using the EVAP purge seal function.
  3. Command the purge open to 20 percent. Seal the EVAP system at -8.00 in H2O.
  4. Exit the system seal.
  5. Verify the scan tool FTP sensor pressure parameter decreases to near 0 in H2O.