Leak Test

The leak test is completed in three steps:

1. To draw the system down to manifold vacuum, the canister close valve shuts and the purge control solenoid valve opens. The fuel tank pressure sensor monitors the rate at which pressure drops in the system.
2. The fuel tank pressure sensor now monitors how well the system holds the vacuum. The purge control solenoid valve closes, completely sealing the system.
3. At the end of the test, the canister close valve opens and the purge control solenoid valve returns to its cycling mode. If the canister close valve is stuck closed, the fuel tank pressure sensor will see that the system remains under a vacuum and code P0446 is set.

Note that water or other debris in the line between the purge control solenoid valve and canister can also set code P0446. If the purge control valve is stuck open, code P0445 may be set. To clear lines of debris, blow compressed air through the lines.