In Reply to: E39 speedometer signal source posted by Gwynne Spencer on December 11, 1999 at 08:38:47:
Acts like a front wheel sensor to me.
I'm stopped. The road is ice. I turn off the DSC and put the car in third gear and drop the clutch and give it gas. The tach zooms to 3,000 rpm, the wheels are spinning like mad, but car is not going forward much at all. WHY is the spedo showing less than 10 mph if the sensor is on the REAR wheel?
: Some time ago there was a discussion on this board about where the speedometer gets it signal. I have the answer from a BMW master technician - this should put this open issue "
: to bed". I will post it below.
: Gwynne Spencer
: The speed signal is picked up by the ABS/ASC/DSC control unit from a rear wheel sensor. It is transmitted to the instrument cluster via the IBus, which in turn, passes it along to any other control units that need it via the KBus.
: The unfortunate part about this system is that there is no longer anywhere to tie in a rally computer, or any other (non BMW) accessory that requires vehicle speed.
: Brett Anderson