Weak Vacuum Test

The weak vacuum tests is for large leaks and blockages in the EVAP system. The PCM will command ON, or close the EVAP vent valve and command ON, or open, the EVAP purge valve with the engine running, allowing the engine vacuum into the EVAP system. The PCM monitors the Fuel Tank Pressure (FTP) sensor in order to verify that the system is able to reach a predetermined level of vacuum within a specific time. If the PCM does not detect the predetermined vacuum level, a DTC P0440 will set.