P0446

SYSTEM DESCRIPTION
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge valve ON and the EVAP canister vent valve ON. This allows a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge valve OFF and the EVAP canister vent valve OFF. The control module monitors 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, this DTC sets.




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
^ DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1106, P1107, P1111, P1112, P1114, P1115, P1121, or P1122 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).
^ The vehicle speed sensor (VSS) is less than 121 km/h (75 mph).

CONDITIONS FOR SETTING THE DTC
^ The FTP is less than -10 in H2O.
^ The condition is present for 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module will illuminate the malfunction indicator lamp (MIL) when the diagnostic test runs and fails.
^ The control module will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module will turn the MIL OFF during the first trip in which the diagnostic has been run and passed.
^ A last test failed (current DTC) clears when the control module turns OFF the MIL.
^ The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
^ The DTC can be cleared by using a scan tool.

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.

TEST DESCRIPTION

Steps 1-9:

Steps 10-15:

The number below refers to the step number on the diagnostic table.
4. This test determines if the FTP sensor is functioning.