P0446

DESCRIPTION
A restricted or blocked Evaporative Emission (EVAP) vent path is detected by the Powertrain Control Module (PCM) 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 PCM 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, Diagnostic Trouble Code (DTC) P0446 will set.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0452, or P0453 are not set.
^ The ignition voltage is between 10-18 volts.
^ The Barometric Pressure (BARO) is more than 75 kPa.
^ The fuel level is between 15-85 percent.
^ The Engine Coolant Temperature (ECT) is between 4-30°C (39-86°F).
^ The Intake Air Temperature (IAT) is between 4-30°C (39-86°F).
^ The start up ECT and IAT are within 9°C (16°F) of each other.
^ The vehicle speed sensor (VSS) is less than 121 kmh (75 mph).

CONDITIONS FOR SETTING THE DTC
^ Fuel tank pressure is less than -10 inch0 H2O.
^ The condition is present for as long as 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The Powertrain Control Module (PCM) will turn OFF the MIL during the first trip in which the diagnostic has been run and passed.
^ The history DTC will clear when the PCM turns OFF the MIL.
^ The DTC can be cleared by using the scan tool.

DIAGNOSTIC AIDS
The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. 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. To repair a blockage in the EVAP system, refer to Evaporative Emission (EVAP) System Cleaning. Service and Repair

TEST DESCRIPTION

Steps 1-10:

Steps 11-20:

The numbers below refer to the step numbers on the diagnostic table.
4. This step checks if the FTP sensor is functioning.
5. This step checks if the condition is present.
6. This step checks the EVAP vent valve electrical operation.
7. This step checks for a restricted EVAP vent valve
8. This step checks if the restriction is in the EVAP canister or the vent hose.