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.

Open circuit between throttle body 6-pin harness connector terminal "E" (Black wire) and PCM 30-pin harness connector terminal "4AB" (Blue/White wire)
Open circuit between throttle body 6-pin harness connector terminal "F" (White/Green wire) and PCM 30-pin harness connector terminal "4Y" (Blue/Black wire)
PCM malfunction
Poor connection of throttle body or PCM harness connectors
Short to ground circuit between throttle body 6-pin harness connector terminal "F" (White/Green wire) and PCM 30-pin harness connector terminal "4Y" (Blue/Black wire)
Short to ground circuit between throttle body 6-pin harness connector terminal "E" (Black wire) and PCM 30-pin harness connector terminal "4AB" (Blue/White wire)
Short to power between throttle body 6-pin harness connector terminal "E" (Black wire) and PCM 30-pin harness connector terminal "4AB" (Blue/White wire)
Throttle valve motor malfunction