System Description

The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller uses this FTP signal to determine atmospheric pressure for use in the engine OFF small leak test, DTC P0442. This DTC will set if the control module detects an intermittent signal from the FTP that would prevent the engine-off small leak test, DTC P0442, from running.