The dash "BRAKE" light will NOT reset by itself or by disconnecting the battery. It MUST be reset by a computer input (dealer, third party, or if you have a later model e90, via your own dash controls)
You should be able to reset the brake light via the dash controls and the steering column stalk. This is the procedure I used successfully:
Insert key into slot
Press start/stop button without depressing clutch/brake and wait for the service reminder to dissapear.
Immediately after service reminder goes out, press and hold the odometer reset. After 3 secs a warning triangle will appear, keep the odo. button pressed and after another 2-3 secs the Oil can will appear. I f you hold it too long (10 secs in total) you will overshoot the runway and some German writing will appear giving the software level/ can bus etc. of the car. Go back to the beginning and start again.
You are now in the service menu, use the toggle switch on indicator stalk to scroll up/down through the various service items.
When you have the item you want to reset showing, press the BC button on end of indicator stalk. Reset should now appear in the display. Press in and hold the BC button for 2-3 secs and a clock will start whirling around and hey presto, its done
You can now either scroll up/down to select another item (as in step 4) or you can press the start/stop button to exit.
I'm not sure of the production date when BMW enabled resetting the "BRAKE" light via the dash/stalk control but the very early e90s did not have this capability.
Last edited by jmd_forest; 10-10-2009 at 08:13 PM.