Possible Causes

WARNING: This page is about a different car, the 2002 Mazda B4000, 2002 Mazda B3000, and 2002 Mazda B2300. However, it is still accessible from the selected car via links, so may be relevant.

Possible causes are:

Open or short in BPP circuit.
Open or short in brakelight circuits.
Damaged PCM.
Malfunction in module(s) connected to BPP circuit.
Damaged brake switch.
Misadjusted brake switch.