Possible Causes

WARNING: This page is about a different car, the 2003 Mazda Protege5 and 2003 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.

Fuel gauge sending unit malfunction.
Open circuit between fuel gauge sending unit and PCM.
Open circuit between ground and fuel gauge sending unit.
PCM malfunction.
Poor connection at fuel gauge sending unit and/or PCM harness connectors.