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Home >> Saturn >> 2009 >> Sky Red Line, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L - DTC P0243 To DTC P0690 >> DTC P0450-P0453 >> Circuit/System Description

Circuit/System Description

The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The engine control module (ECM) 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 ECM also uses this FTP signal to determine atmospheric pressure for use in the engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference it must first be re-zeroed. The sensor performance test includes checks for sudden changes in pressure or signal oscillation and a pressure range check.

This turbocharged engine is equipped with a one way flow check valve that prevents boost pressure form entering the purge line and EVAP system.

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