from what i have read on roadfly.org
"be installed in an 03'745 and will work with factory head unit per Michael, aka "Mat". He told me that BMW did inform him that it would work correctly just like the 04' models. To check this out I contacted Momentum BMW in Houston,TX and they said that they had installed it several times and it works fine. So glad to get a straight answer.
so call your local dealership