P0446
DTC P0446
DTC Descriptor
DTC P0446
- Evaporative Emissions (EVAP) Vent System Performance.
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
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. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, DTC P0446 will set.
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 engine control module (ECM) can report DTC P0446 failed, DTCs P0441, P0442, and P0456 must run and pass.
* DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0141, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0402, P0404, P0405, P0406, P042E, P0444, P0445, P0452, P0453, P0462, P0463, P0502, P1137, and P1138 are not set.
* The ignition 1 voltage is between 10-16 volts.
* The barometric pressure (BARO) is more than 72 kPa.
* The start-up IAT minus the startup ECT is less than 12°C (53°F).
* The start-up ECT minus startup IAT is less than 50°C (122°F).
* The start-up ECT and IAT is between 0° C (32°F) and 40°C (104°).
* The start-up IAT is 3°C (37°F) less than the actual IAT.
* Purge start time is less than 360 seconds.
* Soak time is more than 720 minutes or IAT and ECT less than 12°C difference.
* Engine Run Time is more than 1 second and less than 420 seconds plus Purge start time.
* DTC P0446 runs once an ignition cycle when the above conditions are met.
Conditions for Setting the DTC
* Fuel tank pressure is more than 9.3 mm Hg (8 inch H2O) or less than -4.7 mm Hg (-2.5 inch H2O) at cold engine startup.
* The above condition is present for at least 2 seconds.
Action Taken When the DTC Sets
DTC P0446 is a Type A DTC.
Conditions for Clearing the DTC
DTC P0446 is a Type A 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
DTC Type Reference
Diagnostic Trouble Code (DTC) Type Definitions Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
* Scan Tool Data List Scan Tool Data List
* Scan Tool Data Definitions Scan Tool Data Definitions
* Scan Tool Output Controls Scan Tool Output Controls
Special Tools Required
* 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
* GE-41415-50 Fuel Tank Cap Adapter
Circuit/System Verification
Verify DTC's P0458, P0459, P0498, P0499, P0452, or P0453 are not set.
If a DTC is set refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle
Verify the following conditions do not exist in the EVAP system:
1. Disconnect the purge line from the EVAP purge valve.
2. With a scan tool and the ignition ON observe the fuel tank pressure sensor parameter.
3. Verify the FTP scan tool parameter is 0 in H2O.
4. If not verify the FTP scan tool parameter sensor voltage is more than 4.7 V
• If the FTP sensor voltage is 4.7 V or more go to DTC P0452 or P0453 P0452.
5. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.
Circuit/System Testing
1. Reconnect all previously disconnected EVAP hardware.
2. Ignition OFF. Connect the J 41413-200 power supply clips to a known good 12-volt source
3. Remove the fuel tank filler cap. Install the GE-41415-50 to the fuel fill pipe.
4. Install the fuel tank filler cap to the GE-41415-50 .
5. Ignition ON, engine OFF, with a scan tool, seal the EVAP system.
6. Turn the nitrogen/smoke valve on the EEST to nitrogen.
Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
7. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 in H20.
8. While observing the FTP sensor parameter with a scan tool, command the EVAP vent valve OFF.
9. Verify the FTP Sensor parameter is 0 in H2O.
• If not check for a blockage or restrictions in the EVAP vent hose, or replace the EVAP vent solenoid valve.
Repair Instructions
Perform the Diagnostic Repair Verification Diagnostic Repair Verification after completing the diagnostic procedure.
PSD SIE TITLE Error: SIE linked to empty Cell ID 125178
Repair Verification
1. Ignition ON, engine OFF, with a scan tool, seal the EVAP system.
2. Turn the nitrogen/smoke valve on the EEST 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 in 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 in H2O.