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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 00: Evaporative Emission (EVAP) Vent System Performance

Circuit/System Description

This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The engine control module (ECM) commands the EVAP canister purge solenoid valve open and the EVAP canister 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 canister purge solenoid valve closed and the EVAP canister vent solenoid valve open. The ECM monitors the fuel tank pressure sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 kPa (0 PSI) in a calibrated time, this DTC sets.

Fuel Tank Pressure Sensor Signal Voltage

Fuel Tank Pressure

Low, Approximately 1.5 V or less

Positive Pressure

High, Approximately 1.5 V or more

Negative Pressure / Vacuum

Conditions for Running the DTC
    • DTCsP0449 00, P0451 00, P0452 00, P0453 00, P0454 00, P0498 00, P0499 00, P0562 00, P0563 00, P0642 00, P0643 00 are not set.
    • The ignition voltage is between 10-18 V.
    • The EVAP system is purging.
    • DTC P0446 00 runs once per trip when the above conditions have been met.

Conditions for Setting the DTC
    • The fuel tank pressure sensor is more than 2 kPa (13.7 PSI) vacuum for 2 s during the 13 min test.
        OR
        The fuel tank pressure sensor is less than -0.6 kPa (-4.3 PSI) or more than 1.2 kPa (8.6 PSI) for 3 s after a cold start ignition ON.
    • The fuel tank vacuum is greater than a calibrated amount for a calibrated period of time.

Action Taken When the DTC Sets

DTC P0446 00 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0446 00 is a Type B DTC.

Diagnostic Aids
    • An intermittent condition may be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill condition.
    • An EVAP canister, vent hose, or EVAP canister vent solenoid valve that has restricted flow may cause this DTC to set. Using a EVAP canister purge solenoid valve command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the engine running, the EVAP canister vent solenoid valve open, and the EVAP canister purge solenoid valve commanded to 100%, the fuel tank vacuum should not increase to more than 1.2 kPa (8.6 PSI).
    • An EVAP canister filter that is restricted can cause this DTC to set. Refer to Evaporative Emission Canister Replacement .
    • Disconnecting one component at a time while the EVAP system is under flow will help to pinpoint a restriction in the system.

Reference Information

Connector End View Reference

Component Connector End Views

Description and Operation

Evaporative Emission Control System Description

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • EN 41413-200 Evaporative Emissions System Tester
    • GE 41415-50 Fuel Tank Cap Adapter

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification
  1. Ignition ON and fuel cap removed, verify that the scan tool Fuel Tank Pressure Sensor parameter is between 1.3-1.7 V.
    2. ⇒If not within the specified range, go to the B150 Fuel Tank Pressure Sensor section in Circuit/System Testing.
  2. Install the fuel cap.

    3. Caution: Do not allow the FTP sensor voltage to exceed 4.5 volts or fuel tank damage may occur.

  3. With the engine running, the Q13 Evaporative Emission Vent Solenoid Valve open and the Q12 Evaporative Emission Purge Solenoid Valve commanded to 100%, the fuel tank vacuum should not increase to more than 3 kPa (20.6 PSI).
    4. ⇒If the fuel tank vacuum is greater than the specified range, go to the restriction section in Circuit/System Testing.
  4. 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.

Circuit/System Testing
    • Perform the Circuit/System Verification before proceeding with the Circuit/System Testing.
    • Refer to the EN 41413-200 Evaporative Emissions System Tester operation manual for detailed instructions.

Restriction

With the engine running, the Q13 Evaporative Emission Vent Solenoid Valve open, and the Q12 Evaporative Emission Purge Solenoid Valve commanded to 100%, the fuel tank vacuum should not increase to more than 3 kPa (20.6 PSI).

⇒If the fuel tank vacuum is greater than the specified value, isolate the restriction by disconnecting one component at a time while the Q12 Evaporative Emission Purge Solenoid Valve is commanded to 100% and the vent valve is open.

Fuel Tank Pressure Sensor

  1. Ignition ON and fuel cap removed, verify that the scan tool Fuel Tank Pressure Sensor parameter is between 1.3-1.7 V.
    2. ⇒If the scan tool Fuel Tank Pressure Sensor parameter is not within the specified range, test the B150 Fuel Tank Pressure Sensor low reference circuit for an open or high resistance. If the circuit tests normal, replace the B150 Fuel Tank Pressure Sensor.
  2. With the GE 41415-50 Fuel Tank Cap Adapter, connect the EN 41413-200 Evaporative Emissions System Tester to the fuel filler neck.
  3. Start the engine.
  4. Allow the engine to idle.
  5. Use the purge/seal function to seal the system with a scan tool.
  6. Command the Q12 Evaporative Emission Purge Solenoid Valve to 30%.
  7. Observe the vacuum/pressure gauge on the EN 41413-200 Evaporative Emissions System Tester and the scan tool Fuel Tank Pressure Sensor parameter.
  8. Allow the vacuum to increase on the gauge of the EN 41413-200 Evaporative Emissions System Tester until it reaches approximately 4 kPa (27.4 PSI), or until the vacuum reached the abort limit on the scan tool.
    9. ⇒If the difference between the scan tool Fuel Tank Pressure Sensor parameter and the vacuum/pressure gauge on the EN 41413-200 Evaporative Emissions System Tester more than 1 in, replace the B150 Fuel Tank Pressure Sensor.
    ⇒If the scan tool Fuel Tank Pressure Sensor parameter display was less than 3.2 V, replace the B150 Fuel Tank Pressure Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup and programming

Repair Verification

Note: Larger volume fuel tanks and or those with lower fuel levels may require several minutes for the floating indicator to stabilise.

With the engine running, the Evaporative Emission Vent Solenoid Valve open and the Evaporative Emission Purge Solenoid Valve commanded to 100%, the fuel tank vacuum should not increase to more than 2 kPa (13.7 PSI).

   


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