Possible Causes

WARNING: This page is about a different car, the 2003 Mazda MPV and 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.

Faulty MAF/IAT sensor.
Open between main relay and MAF/IAT sensor.
Open or short MAF/IAT sensor and PCM harness connectors.
Poor connection at MAF/IAT sensor or PCM harness connector terminals.
PCM malfunction.