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
Open circuit in Green/Orange wire between brake switch 4-pin harness connector terminal "A" and PCM 27-pin harness connector terminal "3T"
Open circuit in Black/Orange wire between brake switch 4-pin harness connector terminal "C" and body ground
PCM malfunction
Short circuit to power in Green/Orange wire between brake switch 4-pin harness connector terminal "A" and PCM 27-pin harness connector terminal "3T"
Short to GND circuit in Green/Orange wire between brake switch 4-pin harness connector terminal "A" and PCM 27-pin harness connector terminal "3T"