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:

Brake switch malfunction
Connector or terminal malfunction
Open circuit between positive battery terminal and brake switch 4-pin harness connector terminal "B" (Green/White wire)
Open circuit in Green/Yellow wire between brake switch 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 32
PCM malfunction
Short to power circuit in Green/Yellow wire between brake switch 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 32