The evaporative
emission control system prevents hydrocarbon vapors from escaping from the
fuel tank into the atmosphere where they could form photochemical smog.
Gasoline vapors are collected in the charcoal canister. The Fuel Tank
Pressure Sensor (FTPS) is installed on fuel pump assembly and is an
integral part of the evaporative monitoring system. The ECM monitors the
FTPS signal to detect vacuum decay and excess vacuum. The FTPS measures
the difference between the air pressure inside the fuel tank and
atmospheric air pressure to check the purge control solenoid valve
operation and for leak detection in the evaporative emission control
system by monitoring pressure and vacuum levels in the fuel tank during
the purge control solenoid valve operating cycles.
