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Home >> Saturn >> 2005 >> L300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Diagnosis - (DTC P0446 To DTC P2100) >> DTC Tests >> DTC P0451: FTP Sensor Performance >> Circuit Description

Circuit Description

The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the evaporative emission (EVAP) diagnostic test. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. If the FTP sensor signal voltage is not within a calibrated value range during a cold engine start, this DTC sets.

The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.

DTC P0451

FTP Sensor Signal Voltage Fuel Tank Pressure
High, Approximately 2.5 Volts or More Positive Pressure
Low, Approximately 2.5 Volts or Less Negative Pressure/Vacuum
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