ABS Light.

Subject: ABS Light.
From: Ahsun Murad <murada@domain.elided>
Date: Tue, 23 Jul 1996 15:03:57 -0400
In response to Jay Karolyi's quesion on the ABS idiot light being on all the
time on an 87 325is...

I posted an article on this a few days back. If the light comes on when you
turn the key, and then stays on when you start the car, then I'd say its a
relay - there are two under the ABS hydraulic unit plastic cover. Under normal
operation, when you turn on the ignition, the relays will click a couple of
times - quite audible - as the system undergoes a self-test of the relays and
the circuits. When you start moving, and whenever the vehicle is in motion,
at a speed above a few (<10) miles per hr, the pulses from all the  ABS sensors
are monitored. Missing pulses (eg a broken ABS sensor tip or rusted pulse
wheel) would cause the light to come back on soon after you start moving.

Change the relays - if the light goes out when you start the car, and stays out
when you start moving, you are OK. If it comes back on, check the ABS sensors - 
one on each wheel. The ABS system is designed to operate exactly like in a
non-ABS equipped car in the event a system fault is detected, so it is not
dangerous.

Ahsun Murad
88 M5
86 528e