I did find this on a Mazda forum:
TCM U0100, RAW: C100, Meaning: Lost Communication With ECM / PCM A"
but none of my other information gives any information on this code. If you have your car at a repair shop and they are stumped there is a professional service called Identafix. http://www.identifix.com/info/about_us.htm They only deal with professional repair shops. They are in the Minnesota 651-633-8007 begin_of_the_skype_highlighting 651-633-8007 end_of_the_skype_highlighting. Your auto repair shop do all their diagnosis tests, and discuss your problem with a team of professional technicians great service cheap and very bright people.If the repair shop that are repairing your car are stumped this is a great service. This company only deal with automotive repair shops and don't answer questions for the general public but are an amazing knowledge base.
If you do not properly warm up the 2004 rotary engine in this car ( and I mean actually driving it) until proper driving temp, it will flood. Happened to me 2 times within 3 months. The first time I didn't know better and just let it idle to warm. 2nd time my friend was convinced he could move it from outside the garage to inside the garage in a snowstorm. The second time around, I learned how to deflood my own engine b/c repairs are about $700-800 :-( to basically replace 4 spark plugs.