Fuel Tank Pressure Sensor

The display shows pressure from -17.5 in. H2O to 7.5 in. H2O and from 0 to 5.1 volts. Fuel tank pressure is obtained from the EVAP Pressure sensor. The EVAP Pressure sensor is used during the PCM's diagnosis of the EVAP system. The EVAP Pressure sensor is a sensor that changes resistance based upon fuel tank pressure (or vacuum). A vacuum is considered negative pressure. The PCM provides a 5 volt reference and ground. The EVAP Pressure sensor signal varies between ground and 5 volts as fuel tank pressure varies. As pressure decreases (negative pressure, or vacuum), voltage increases. As pressure increases, voltage decreases (positive pressure, low voltage). The PCM uses the EVAP Pressure sensor values as an indicator of EVAP system efficiency.