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:

Connector or terminal malfunction
PCM malfunction
PSP switch malfunction
Short to ground circuit between PSP switch harness connector terminal "A" (Brown/Green wire) and PCM 104-pin harness connector terminal No. 14 (Black/Blue wire)