• Perform the Diagnostic System Check prior to using this diagnostic procedure:Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis:Strategy Based Diagnosis
• An overview of each diagnostic category can be found here:Diagnostic Procedure Instructions

For an overview of the component/system, refer to:Evaporative Emission Control System Description

This diagnostic tests the Evaporative Emission (EVAP) System for a restricted or blocked EVAP vent path that would cause excess amounts of vacuum to develop in the EVAP system.

• DTCs related to the following system/component = Not Set
• B34 Engine Coolant Temperature Sensor
• B46 Fuel Level Sensor
• B66 Intake Air Temperature Sensor
• B74 Manifold Absolute Pressure Sensor
• B75B Mass Air Flow/Intake Air Temperature Sensor
• B115 Vehicle Speed Sensor
• B150 Fuel Tank Pressure Sensor
• Q12 Evaporative Emission Purge Solenoid Valve
• Q13 Evaporative Emission Vent Solenoid Valve
• Q38 Throttle Body
• Evaporative Emission (EVAP) Purge System
• Fuel Pump
• Output Speed Sensor
• Reduced Engine Power
• Throttle Position Sensor
• Barometric Pressure Sensor=Greater than 70 kPa (10.15 PSI)
• Fuel Level Sensor=10 to 90%
• Start-Up Engine Coolant Temperature Sensor=Less than 35°C (95°F)
• Start-Up Intake Air Temperature Sensor=4 to 35°C (39 to 95°F)
• System Voltage=Greater than 10.0 V

Frequency the DTC runs=Once—Per cold start-up—After the running conditions are met

Fuel Tank Pressure Sensor=Greater than 4.65 mmHg (2.5 in. H2O)orLess than −1.24 mmHg (−5.0 in. H2O)—For greater than 60 s

or

Fuel Tank Pressure Sensor=Less than −22.5 mmHg (−12.0 in. H2O)—For greater than 5 s—Before 6.0 L (1.6 gal) of vapor have been purged through the EVAP system.

DTCs listed in the DTC Descriptor category=Type B DTC

DTCs listed in the DTC Descriptor category=Type B DTC

The following conditions could cause DTC P0446 to set:

• Cold Regions=Ice/Snow@Evaporative Emission Vent FilterorEvaporative Emission Canister Air Inlet Hose
• Dry Regions=Dirt/Dust/Sand@Evaporative Emission Vent FilterorEvaporative Emission Canister Air Inlet Hose
• Wet Regions=Mud@Evaporative Emission Vent FilterorEvaporative Emission Canister Air Inlet Hose

Master Electrical Component List

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References

• CH-41415-30 - Fuel Tank Cap Adapter
• GE-41413-A / B / C - Evaporative Emissions System Tester (EEST)
• GE-41415-60 - Engine Induction System Leak Test Adapter/Capless Fuel Fill Adapter

Equivalent regional tools:Special Tools

1. Ignition » On / Vehicle » In Service Mode
2. Verify DTC P0449, P0498, P0499, P0451–P0454 is not set
• If any of the DTCs are set

  Refer to:Diagnostic Trouble Code (DTC) List - Vehicle.

• If none of the DTCs are set
3. Ignition/Vehicle » Off
4. Perform the following action:
• {Cap Type Fuel Fill}Remove»Fuel Tank Filler Cap
• {Capless Type Fuel Fill}Install»GE-41415-60 - Engine Induction System Leak Test Adapter/Capless Fuel Fill Adapter@Door@Fuel Tank Filler Pipe
5. Ignition » On / Vehicle » In Service Mode
6. Verify the scan tool parameter:Fuel Tank Pressure Sensor=1.3 to 1.7 V
• If not between 1.3 and 1.7 V

  Refer to:DTC P0451-P0454.

• If between 1.3 and 1.7 V
7. Perform the following action:
• {Cap Type Fuel Fill}Install»Fuel Tank Filler Cap
• {Capless Type Fuel Fill}Remove»GE-41415-60 - Engine Induction System Leak Test Adapter/Capless Fuel Fill Adapter@Door@Fuel Tank Filler Pipe
8. Engine » Idling — At normal operating temperature
9. Perform the scan tool function:EVAP Purge Solenoid Valve»50%

   Verify the scan tool parameter:Fuel Tank Pressure Sensor=Less than 2.5 V

• If 2.5 V or greater

  Refer to: Circuit/System Testing

• If less than 2.5 V
10. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

    Verify the DTC does not set.

• If the DTC sets

  Refer to: Circuit/System Testing

• If the DTC does not set
11. All OK.

1. Verify the following conditions do not exist:
• Q13 Evaporative Emission Vent Solenoid Valve—Blocked/Restricted/Visible Damage
• Evaporative Emission Canister—Blocked/Defective/Restricted/Visible Damage
• Evaporative Emission Canister Purge Hose—Blocked/Defective/Incorrect connection/Kinked/Restricted/Visible Damage
• Evaporative Emission Canister Vent Hose—Blocked/Defective/Incorrect connection/Kinked/Restricted/Visible Damage
• Evaporative Emission Canister Vent Pipe—Blocked/Defective/Incorrect connection/Kinked/Restricted/Visible Damage
• Evaporative Emission Vent Filter—Blocked/Dirty/Restricted/Visible Damage
• If a condition exists

  Repair or replace as necessary

• If no condition exists
2. Install any previously removed components.
3. Perform the following action:
• {Cap Type Fuel Fill}Remove»Fuel Tank Filler Cap

  Install»CH-41415-30 - Fuel Tank Cap Adapter

• {Capless Type Fuel Fill}Install»GE-41415-60 - Engine Induction System Leak Test Adapter/Capless Fuel Fill Adapter@Door@Fuel Tank Filler Pipe
4. Perform the following action:
• {Cap Type Fuel Fill}Install»GE-41413-A / B / C - Evaporative Emissions System Tester (EEST)—Hose@CH-41415-30 - Fuel Tank Cap Adapter
• {Capless Type Fuel Fill}Install»GE-41413-A / B / C - Evaporative Emissions System Tester (EEST)—Hose@GE-41415-60 - Engine Induction System Leak Test Adapter/Capless Fuel Fill Adapter
5. Ignition » On / Vehicle » In Service Mode

Note:

• Before proceeding with this test, review the tool user manual for Safety Information and Instructions:GE-41413-A / B / C - Evaporative Emissions System Tester (EEST)
• The user manual that is supplied with the tool, is also available online, refer to:GM Special Service Tools
• Make sure the underbody temperature of the vehicle and the tester temperature are similar.
• Completely unwind the nitrogen/smoke hose from the bracket to optimize the tester's performance.

6. Perform the following action:
1. Select»Nitrogen@GE-41413-A / B / C - Evaporative Emissions System Tester (EEST)
2. Perform the scan tool function:EVAP Vent Solenoid Valve»Not Venting
3. Press and release the switch:Remote Switch@GE-41413-A / B / C - Evaporative Emissions System Tester (EEST)—Special Tool=OnorActivated

Note: Do NOT exceed the specified value or incorrect test results may occur.

4. Use the tool to achieve a gauge reading of 9.3 mmHg (5.0 in H2O)
7. Perform the scan tool function:EVAP Vent Solenoid Valve»Venting

   Verify the scan tool parameter:Fuel Tank Pressure Sensor=0.0 mmHg (0.0 in. H2O)

• If not the specified value
1. Ignition/Vehicle » Off
2. Verify the following conditions do not exist:
• Q13 Evaporative Emission Vent Solenoid Valve—Blocked/Restricted/Visible Damage
• Evaporative Emission Canister—Blocked/Defective/Restricted/Visible Damage
• Evaporative Emission Canister Purge Hose—Blocked/Defective/Incorrect connection/Kinked/Restricted/Visible Damage
• Evaporative Emission Canister Vent Hose—Blocked/Defective/Incorrect connection/Kinked/Restricted/Visible Damage
• Evaporative Emission Canister Vent Pipe—Blocked/Defective/Incorrect connection/Kinked/Restricted/Visible Damage
• Evaporative Emission Vent Filter—Blocked/Dirty/Restricted/Visible Damage
• If a condition exists » Repair or replace as necessary
• If no condition exists
3. Replace the component:Q13 Evaporative Emission Vent Solenoid Valve
• If the specified value
8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

   Verify the DTC does not set.

• If the DTC sets

  Repeat the procedure starting at step 1

• If the DTC does not set
9. All OK.

Perform the Diagnostic Repair Verification after completing the repair:Diagnostic Repair Verification

• Evaporative Emission Canister Replacement
• Evaporative Emission Canister Vent Solenoid Valve Replacement—Q13 Evaporative Emission Vent Solenoid Valve