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 P0451, P0452, and P0453 must run and pass.
* DTC P0100, P0101, P0102, P0103, P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0125, P0128, P0221, P0222, P0223, P0443, P0449, P0451, P0452, P0453, P0458, P0459, P0496, P0498, P0499, P0560, P0562, P0563, P0700, P2122, P2123, P2127, P2128 or P2138 is not set.
* The ignition voltage is greater than 10 volts.
* The fuel system is operating in Closed Loop.
* The engine run time is greater than 10 minutes or the fuel trim is stable.
* The engine is idling.
* The FTP is between -18.7 and +7.5 mm Hg (-10.0 and +4.0 in. H2O).
* The ambient air temperature (AAT) is between 2-32°C (35-90°F).
* The ECT and the AAT are within 10°C (18°F) of each other at engine start-up.
* The fuel level is between 12-88 percent.
* The vehicle speed sensor (VSS) is less than 2 km/h (3 mph).
* The above conditions exist for greater than 5 seconds.
* 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 FTP is less than -6.0 mm Hg (-3.2 in. H2O).
* The condition is present for greater than 4 seconds or a cumulative of 50 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 Testing
1. Verify DTC P0458, P0459, P0498, P0499, P0452, or P0453 is not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) .
2. Disconnect the purge line from the EVAP purge valve.
3. Ignition ON, observe the fuel tank pressure sensor parameter with a scan tool. The FTP sensor parameter should be 0 inches H2O. If the pressure is not at 0 inches H2O, verify the FTP sensor voltage is less than 4.7 volts.
• If the FTP sensor voltage is greater than 4.7 volts, refer to DTC P0452 or P0453 (P0452) .
4. Reconnect all previously disconnected EVAP hardware.
Important: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.
5. 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 .
6. Ignition ON, seal the EVAP system with a scan tool.
7. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen.
Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
8. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 inches H20.
9. While observing the FTP sensor parameter with a scan tool, 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 replace the EVAP vent solenoid valve.
10. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records data.
Repair Instructions
Evaporative Emission Hoses/Pipes Replacement - Chassis/Canister (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.
Important: 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. While observing the FTP sensor parameter with a scan tool, command the EVAP vent valve OFF.
5. Verify the FTP Sensor parameter is 0 inches H2O.