Possible Causes

WARNING: This page is about a different car, the 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Possible causes are:

APP sensor malfunction
Connector or terminal malfunction
Open circuit in Red/Green wire between APP sensor 6-pin harness connector terminal "E" and PCM 27-pin harness connector terminal "3A"
Open circuit in White wire between APP sensor 6-pin harness connector terminal "F" and PCM 27-pin harness connector terminal "3D"
Short to constant voltage supply circuit in White wire between APP sensor 6-pin harness connector terminal "F" and PCM 27-pin harness connector terminal "3D"