Weak Vacuum Tests

TEST DESCRIPTION

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 perform will perform the following:

1. Command the EVAP vent valve ON (closed).
2. 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:

^ Store a DTC P0440 after the first failed test.
^ Store the data in the Freeze Frame and the Failure Records.
^ Turn the 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:

^ While the EVAP vent valve is ON (closed), turn the [1][2]EVAP purge valve OFF (closed) and Run the Small EVAP Leak Test.
^ Run the Purge Valve Leak Test, if the first Weak Vacuum Test passes.
^ Turn the MIL OFF, 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.