So I compared both key fobs. When I normally press the button on the bad key fob, it doesn't light up. When I hold it down for a little longer there is a flash, but it is delayed where as in the good fob as soon as I press the button the light flashes.
All I know is the fob has lock, unlock, trunk and panic on it. Don't know much about DAS3 etc.
1995 M3...my baby.