P0446
DTC P0446
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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.
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.
Conditions for Running the DTC
* Before the ECM can report DTC P0446 failed, DTCs P0450, P0452, and P0453 must run and pass.
* The ambient air temperature (AAT) is between 2-32°C (35-90°F).
* The closed loop fuel control is active and the short term/long term fuel trims are stabile
* The engine has cycled ON and OFF greater than 6 to 16 times dependent on coolant temperature.
* The FTP is between -26.2 and +10.5 mm Hg (-14.0 and +5.6 in. H2O).
* The fuel level is between 12-88 percent.
* The ECT and the IAT are within 10°C (18°F) of each other at engine start-up.
* The barometric pressure (BARO) is greater than 68 kPa.
* The ignition voltage is between 10-18 volts.
* The fuel system is operating in Closed Loop.
* The vehicle speed sensor (VSS) is within 19-100 km/h (12-62 mph).
* The conditions above exist for approximately 10 minutes.
* DTC P0446 will attempt to run up to 10 times or until the test completes successfully once per ignition cycle.
Conditions for Setting the DTC
* The ECM detects that the FTP is less than -16.4 mm Hg (-8.8 in. H2O) with EVAP vent solenoid valve commanded OFF.
* The condition is present for greater than 4 seconds.
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 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
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Evaporative Emission Control System Description (Evaporative Emission Control System Description)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Special Tools
* 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
* CH-48096 EVAP Service Port Access Tool
* GE-41415-50 Fuel Tank Cap Adapter
Circuit System Verification
1. Ignition OFF, remove the fuel filler cap.
2. Ignition ON, observe the FTP sensor parameter with a scan tool. Verify the FTP sensor is at 0 inches H2O.
3. If not the specified value refer to DTC P0452 or P0453 (P0452).
4. Install the fuel filler cap. Ignition ON, command the EVAP purge solenoid to 50 % with a scan tool. You should hear an audible click.
• If the EVAP purge solenoid does not respond to the scan tool commands, refer to DTC P0443, P0458, or P0459 (P0443).
5. Command the EVAP vent valve ON and OFF with a scan tool. You should hear an audible click.
• If the EVAP vent valve does not respond to the scan tool commands, refer to DTC P0449, P0498, or P0499 (P0449).
6. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, open the hood to disable the Auto-Stop function.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to DTC P254F (P254F).
Note: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.
3. Remove the fuel fill cap and connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
4. Ignition ON, seal the EVAP system with a scan tool.
5. Turn the nitrogen/smoke valve on the J 41413-200 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 J 41413-200 and pressurize the fuel tank with nitrogen to 5 inches H20.
7. Observe the scan tool FTP sensor parameter, command the EVAP vent valve OFF. Verify the FTP Sensor parameter is 0 inches H2O.
• If not the specified value, test for a blockage or a restriction in the EVAP vent hose or inlet. If the components test normal, replace the EVAP vent solenoid valve.
Repair Instructions
Evaporative Emission Canister Vent Solenoid Valve Replacement (Service and Repair)
Repair Verification
1. Ignition ON, seal the EVAP system with a scan tool.
2. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen.
Note: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
3. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 inches H20.
4. Observe the scan tool FTP sensor parameter, command the EVAP vent valve OFF.
5. Verify the FTP Sensor parameter is 0 inches H2O.