Diagnostic Aids
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
A short to ground causing the EVAP vent solenoid ON, will cause the vent valve to close. This will cause DTC P0446 to set.
ECM uses fuel tank pressure sensor to detect amount of vacuum pulled on EVAP system during leak diagnostic tests. Ensure fuel pressure sensor is not skewed by verifying FUEL TANK PRESS. SENSOR on scan tool is 1.3-1.6 volts with ignition on and fuel cap removed.
A faulty main relay will cause DTC P0446 to set.
Check for kinked, pinched or plugged EVAP vent solenoid hose, EVAP vent solenoid stuck in closed position or EVAP canister restricted.