• 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.

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) uses the fuel tank pressure sensor to monitor EVAP system vacuum. With the purge valve and vent valve open, if the EVAP system vacuum goes above a calibrated threshold, P0446 will set.

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

• DTCs P0068, P00C8, P00C9, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0121, P0122, P0123, P0128, P0191, P0192, P0193, P0222, P0223, P0443, P0601, P0604, P0606, P16A0, P16A1, P16A2, P16F3, P2101, P2135, P2176, are not set.
• The ignition voltage is between 11–32 V.
• The barometric pressure (BARO) is more than 70 kPa.
• The fuel level is between 10–90%.
• The startup engine coolant temperature (ECT) is less than 35°C (95°F).
• The startup intake air temperature (IAT) is between 4–30°C (39–86°F).
• DTC P0446 runs once per cold start, for up to 17 min, when the above conditions are met.

• If fuel tank pressure sensor reading is greater than 2.5 in H2O of pressure or less than –5 in H2O of vacuum for 60 s.

  OR

• If fuel tank pressure sensor reading is less than -12 in H2O of vacuum for 5 s before 10 L (2.6 gal) of purge volume.
• After setting the DTC for the first time, 2 L (0.5 gal) of fuel must be consumed before setting the DTC for the second time.

DTC P0446 is a Type B DTC.

DTC P0446 is a Type B DTC.

• An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system may also cause a poor fuel fill condition.
• An EVAP canister filter that is restricted can cause this DTC to set.

Engine Controls Schematics

Master Electrical Component List

Evaporative Emission Control System Description

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References for scan tool information

• CH-41415-30 Fuel Tank Cap Adapter
• GE-41413-A Evaporative Emissions System Tester

For equivalent regional tools, refer to Special Tools

1. Ignition ON.
2. Verify DTC P0443 is not set.
• If the DTC is set

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

• If the DTC is not set
3. Ignition OFF, remove the fuel tank filler cap. Ignition ON.
4. Verify the scan tool Fuel Tank Pressure Sensor parameter is between 1.3–1.7 V.
• If not between the 1.3–1.7 V

  Refer to P0452, P0453 within DTC P0451-P0454.

• If between the 1.3–1.7 V
5. Install the fuel tank filler cap. Engine idling at operating temperature for 5 min.
6. Verify the scan tool Fuel Tank Pressure Sensor parameter does not increase to greater than 2.5 V when commanding the EVAP Purge Solenoid Valve to 50%.
• If greater than 2.5 V

  Refer to Circuit/System Testing.

• If 2.5 V or less
7. 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.
• If the DTC sets

  Refer to Circuit/System Testing.

• If the DTC does not set
8. All OK.

1. Test for a blockage or restrictions in the EVAP system components listed below and repair as necessary.
• Evaporative Emission Vent System Hoses
• Evaporative Emission Canister
• Q13 Evaporative Emission Vent Solenoid Valve
• Evaporative Emission Vent Filter
2. Reconnect all previously disconnected EVAP hardware.

Note: Refer to the GE-41413-A operation manual for detailed instructions in Evaporative Emission Control System Diagnosis.

3. Remove the fuel fill cap and connect the CH-41415-30 to the fuel tank filler neck. Connect the GE-41413-A to the CH-41415-30.
4. Command the EVAP Purge/Seal function to System Seal with a scan tool to seal the EVAP system.
5. Turn the nitrogen/smoke valve on the GE-41413-A to nitrogen.

Note: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

6. Use the remote switch to activate the GE-41413-A and pressurize the fuel tank to 5.0 in H2O.
7. Verify the scan tool Fuel Tank Pressure Sensor parameter is 0 in H2O when commanding the EVAP Vent Solenoid Valve to OFF.
• If not 0 in H20

  Test for a blockage or a restriction in the EVAP vent hose or inlet. If the inlet or hose test normal, replace the Q13 Evaporative Emission Vent Solenoid Valve.

• If 0 in H2O
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.
• If the DTC sets

  Refer to step 1 above.

• If the DTC does not set
9. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

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