P0446

Diagnostic Chart:

Schematic:

The evaporative emission system is tested with on-board diagnostics by applying pressure (vacuum) to system and monitoring pressure decay. The PCM monitors vacuum level through fuel tank vapor pressure sensor. At the appropriate time, EVAP vent solenoid is commanded closed (normally open valve) and EVAP purge solenoid is commanded to a fixed duty cycle, allowing engine to draw a vacuum on entire evaporative emission system. After a calibrated vacuum level is achieved, EVAP purge solenoid is turned off, sealing system. A restricted or blocked EVAP canister path is detected by opening or releasing vent solenoid and monitoring for a rapid decay in pressure. With EVAP vent solenoid open, any vacuum in system should release rapidly unless path is blocked. A blockage can be caused by the following conditions:
^ Faulty EVAP vent solenoid.
^ Plugged, kinked or pinched vent nose.
^ Shorted EVAP vent solenoid driver circuit (should set DTC P1640).
^ Plugged EVAP canister.

DTC PARAMETERS
^ Throttle angle between 7% and 35%.
^ Baro is greater than 75 kPa.
^ Both ECT and IAT are between 4°C (39°F) and 30°C (86°F) at engine start up.
^ ECT is not more than 8°C (14°F) greater than IAT at startup.
^ EVAP purge solenoid is enabled.
^ Fuel tank level is between 15% and 85%.
^ Vehicle speed is less than 113 km/h (70 mph).
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0452, P0453, P0502, P0503, P0601, P0602, P1133 and P1621 are not set.
^ The EVAP system is unable to release vacuum within a given time.

DIAGNOSTIC AIDS
Check for the following conditions:
^ Kinked, pinched, or plugged EVAP vent solenoid hose.
^ EVAP vent solenoid stuck in closed position.