Circuit Description

The DTC P0451 Fuel Tank Pressure (FTP) Sensor Performance diagnostic checks accuracy of FTP sensor signal. Evaporative Emission (EVAP) control system prevents emission of fuel vapors. The fuel vapor generated in the fuel tank while driving or idling enters EVAP canister where a charcoal element absorbs and stores fuel vapor. When certain engine operating conditions are met, Powertrain Control Module (PCM) purges EVAP canister of stored vapors by turning ON EVAP canister purge valve.

Emissions laws require that PCM detect any leakage within EVAP system. PCM monitors EVAP system for leaks by controlling and observing vapor pressures in EVAP system. FTP sensor is used to detect any unexpected pressure in EVAP system. PCM supplies a 5-volt reference and an electrical ground to FTP sensor. FTP sensor contains a silicone based chip that changes electrical resistance when pressure is applied. The sensor converts positive or negative pressure into an electrical signal and sends the signal to the PCM. See FUEL TANK PRESSURE SENSOR OPERATION  table.