Circuit Description

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 engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic test. The ECM supplies a 5 volt reference and a low reference circuit to the FTP sensor. If the ECM detects that the FTP sensor signal voltage is too low, this DTC sets.

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