Circuit Description

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The DTC P0450 Fuel Tank Pressure (FTP) Sensor Circuit diagnostic monitors FTP sensor voltage. Evaporative Emission (EVAP) control system prevents emission of fuel vapors. Fuel vapor generated in 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.

FUEL TANK PRESSURE SENSOR OPERATION

Fuel Tank Vapor Space	FTP - In. Hg	FTP Signal Voltage
Pressure	Positive Value	High
No Pressure	Near Zero	3.0-3.6 Volts
Vacuum	Negative Value	Low