Weak Vacuum Tests

The Weak Vacuum Test is performed by the control module in order to determine if the [1][2]EVAP control system is capable of achieving a sufficient vacuum in the system. During the normal purging of the EVAP control system, the control module will perform the following:
^ Command the EVAP vent valve ON or closed
^ Monitor the fuel tank pressure sensor signal If the control module determines that sufficient vacuum is not achieved, the control module will perform the following steps:
^ Store a DTC P0440 after the first failed test
^ Store the data in the Freeze Frame and Failure Records
^ Turn the Malfunction Indicator Lamp (MIL) ON after a second consecutive failed test

If the control module determines that sufficient vacuum is achieved, the control module will perform the following steps:
^ While the EVAP vent valve is ON or closed, turn the EVAP purge solenoid OFF or closed, and run the Small [1][2]EVAP Leak Test.
^ Run the Purge Solenoid Leak Test if the first Weak Vacuum Test passes.
^ Turn OFF the MIL, if the MIL is ON because of a previous failed Weak Vacuum Test.
^ Clear the data stored in the Freeze Frame for the DTC P0440.

The Weak Vacuum Tests will not run unless the Loaded Canister Test has run and failed.