P0446
DTC P0446
DTC DESCRIPTOR
DTC P0446
Evaporative Emissions (EVAP) Vent System Performance
DIAGNOSTIC FAULT INFORMATION
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
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 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.
- DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0221, P0222, P0223, P0443, P0449, P0458, P0459, P0496, P0498, P0499, P0560, P0562, P0563, P0722, P0723, P2122, P2123, P2127, P2128 and P2138 are not set.
- The ignition 1 voltage is more than 10.5 volts.
- The fuel system is operating in Closed Loop.
- The engine run time is more 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 more than 5 seconds.
- DTC P0446 will attempt to run up to 10 times or 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 more 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.
CIRCUIT/SYSTEM TESTING
1. Inspect the evaporative emission (EVAP) system for the following conditions:
- A damaged EVAP vent valve
- A collapsed or restricted EVAP vent hose/pipe (if equipped)
- A damaged EVAP canister
- If you find any of the above conditions, repair as necessary.
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 P0453. P0453
4. Connect all previously disconnected EVAP hardware.
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.
IMPORTANT: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.
6. Lower the EVAP purge canister to gain access to the EVAP vent inlet, and seal it, using a suitable plug or a plug from the J 41413-300.
7. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen.
8. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 inches H20.
IMPORTANT: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
9. While observing the FTP sensor parameter with a scan tool, remove the EVAP vent valve plug. Verify the FTP Sensor parameter is 0 inches H2O.
- If the FTP is not at the specified range, test for a blockage or a restriction in the EVAP vent hose.
10. If all hoses/pipes test OK, replace the EVAP vent solenoid valve
REPAIR INSTRUCTIONS
- Evaporative Emission Canister Replacement
- Evaporative Emission Canister Vent Solenoid Valve Replacement
- Fuel Tank Pressure Sensor Replacement
REPAIR VERIFICATION
1. Lower the EVAP purge canister to gain access to the EVAP vent inlet, and seal it, using a suitable plug or a plug from the J 41413-300.
2. Turn the nitrogen/smoke valve on the J 41413-200 to nitrogen.
3. Use the remote switch to activate the J 41413-200 and pressurize the fuel tank with nitrogen to 5 in H20.
IMPORTANT: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.
4. While observing the FTP sensor parameter with a scan tool, remove the EVAP vent valve plug.
5. Verify the FTP Sensor parameter is 0 in H2O.