'99 528i ABS/Spedo issues

This appears to be a common set of problems!

In my case, all works when the car is cold, then progressively fails as I drive and/or the weather heats up. First to fail is the Tracs/ABS, and if I happen to be braking when it dies, I get the brake system pulsing expected from an ABS stop. I take that (hopefully!) to indicate that a wheel speed sensor is opening up. Happens sooner in stop-n-go traffic, where there's a lot of braking effort, and in hot weather.

Some time later, say within a mile or two, the speedo quits. CEL never comes on under either failure. Along with the speedometer, I lose the odometer of course, and the MPG "gauge". The fuel-remaining computer still works, but there is no damping on tank slosh; with braking, the mileage goes up, and down under acceleration...

Which wheel sensors control which services?
Is there a way to electrically check the sensor (I imagine it's a coil, responding to a magnet on the hub)? What's the best place to plug in to check them?

Thanks!

Dave

LH rear wheel speed sensor is for the speedomeer.change it and you're done.

Thanks, Moots, but does that also control the ABS/Tracs?
It seems like the failure is progressive (1-10 minutes apart), so I figured there were two units failing.

Tonight, for example, after about 4-5 miles, the ABS/Tracs error light came on. 5 minutes later, the speedometer dropped to zero.

Dave

these wheel speed sensors are dual function sensors.all 4 wheels have wheel speed sensors that inputs the ABS obviously.the lh rear also inputs the speedometer.the other sensors also inputs other systems but i can't remember.google is your best friend.

http://www.bimmerfest.com/forums/sho....php?p=3774725