Im going to hopefuly help alot of people out, but at the same time will upset Mazda dealers.
I have the code to unlock Mazda radios the have 'ERR' due to 3 wrong codes. Do not listen to mazda book that states 3 wrong codes make CD playing Inop req replacement...
121 Metro DW10*2 > 203028, MX5 NB30P2,
Milennia,323 BJ10*2, 626 GF10S2, Tribute.
Step one:- press one at a time- preset 6, AM, Auto M, Seek ^ (up).
Step Two:-Input this number, 4989.
Step Three:- Press and hold Auto M and Preset 6 together.
Step Four:- The Word 'GOOD' will appear on the screen indicated that the radio will work.
Step Five:- Reprogram new Antitheft code into radio as per instrution manual.
Hope this helps some people out, save you some money as so.