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.

BARO sensor malfunction
Connector or terminal malfunction
Open circuit in Brown wire between BARO sensor 3-pin harness connector terminal "B" and PCM 30-pin harness connector terminal "2H"
Open circuit in Pink wire between BARO sensor 3-pin harness connector terminal "A" and PCM 30-pin harness connector terminal "1G"
PCM malfunction
Short circuit to power in Pink wire between BARO sensor 3-pin harness connector terminal "A" and PCM 30-pin harness connector terminal "1G"