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P0446




DTC P0446

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0446

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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.






Conditions for Running the DTC

Note:
The following conditions must be met prior to ignition OFF.

* DTCs P0106, P0107, P0108, P0112, P0113, P0114, P0116, P0117, P0118, P0122, P0123, P0222, P0223, P0443, P0449, P0451, P0452, P0453, P0454, and P2135 are not set.

* The ignition voltage is between 11-32 V.

* The barometric pressure (BARO) is greater than 70 kPa (10.15 PSI).

* The start up Engine Coolant Temperature (ECT) is less than 35°C (95°F).

* The start up Intake Air Temperature (IAT) is between 4-30°C (40-86°F).

* The purge enable time is less than predetermined value based on startup ECT.

* The fuel level is between 10-90%.

* The engine run time is between 1-360 s plus purge enable time.

* 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 27 kPa (3.9 PSI) at cold engine startup.

* The above condition is present for at least 5 s.

Action Taken When the DTC Sets

DTC P0446 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0446 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 (0.2 PSI).

* An EVAP canister filter that is restricted can cause this DTC to set. Refer to Evaporative Emission Canister Replacement Service and Repair.

* 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 Fuel Pump and Level Sensor Assembly

Description and Operation

Evaporative Emission Control System Description Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References 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 Tools and Equipment.

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.

• If not within the specified range, go to the B150 Fuel Tank Pressure Sensor section in Circuit/System Testing.

2. Install the fuel cap.

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 -2 kPa (-0.3 PSI).

• 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 Testeroperation 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 -2 kPa (-0.3 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.

• 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 Testerto 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 Testerand 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 Testeruntil it reaches approximately 4 kPa (27.4 PSI), or until the vacuum reached the abort limit on the scan tool.

• 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 Testermore than 1 kPa (0.1 PSI), 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 Verification Tests after completing the diagnostic procedure.

Control Module References Control Module References for ECM replacement, programming and setup

Repair Verification

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

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 (-0.3 PSI).

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