Circuit/System Description
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the fuel tank pressure. The powertrain control module (PCM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The PCM supplies a 5-volt reference and a low reference circuit to the FTP sensor.
The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.
DTC P0451 or P0454
| FTP Sensor Signal Voltage | Fuel Tank Pressure |
|---|---|
| High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum |
| Low, Approximately 1.5 Volts or Less | Positive Pressure |