DTC P0450 - Fuel Tank Pressure Sensor Malfunction: Condition

WARNING: This page is about a different car, the 1997 Mazda Millenia. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when fuel tank pressure sensor input voltage to ECM is less than .2 volt or greater than 4.9 volts with ignition switch on and engine at normal operating temperature. Possible causes are:

Fuel tank pressure sensor malfunction.
Open or short circuit between terminal "C" on fuel tank pressure sensor and terminal No. 3A on Engine Control Module (ECM).
Open or short circuit between terminal "A" on fuel tank pressure sensor and terminal No. 3F on Engine Control Module (ECM).
Open circuit between terminal "B" on fuel tank pressure sensor and terminal No. 3AB on Engine Control Module (ECM).