ABS Wheel Sensor Resistance:

[BMWLOCO]

ALCON,

I'm still trying to diagnose the ABS light on my E30. I pulled the Relay and took it apart, but didn't notice any link blown. (Attached). I pulled each wheel sensor, cleaned them and unplugged/tested them individually and still the light remained on.

I'm thinking.... since both the front wheel connectors are deteriorated and crumbled, I might not have the proper wires/leads connected to each other. It might be sending the wrong signal to the system.

Does anyone have the resistance numbers so I can ensure they are connected properly.

Thanks in advance.

P.S. is this the proper ABS Relay?

[jlevie]

Troubleshooting the ABS system isn't very difficult. It is a standalone system
that only gets input data from the brake light switch, wheel sensors, and
system power. The parts of the system are the ABS module located next to the
steering column, the ABS relay mounted above the ABS module, the ABS unit in
the left front of the engine bay, and a speed sensor at each wheel.

If the ABS light comes on with ignition, but doesn't go out when the engine
starts, a wiring problem, bad module, or bad ABS relay are the likely
candidates. A failed or weak alternator will also cause this because the
system voltage won't rise enough. There is a fusible link inside the ABS relay
that can be blown. The relay can be repaired, or better yet, replaced.

If the ABS light comes on when you turn on the ignition, goes out when the
engine starts, and then comes back on before the car is moving the cause could
be a bad module, a bad ABS unit, or a wiring fault.

If the light goes out after engine start and only comes on when the car is
moving, there's a problem with one (or more) of the sensors. The simple test
to find out which sensor(s) is the cause is to disconnect all but one of the
sensors and drive the car. If the light comes on, that sensor is sending a
speed signal to the ABS and is good. Repeat with each other sensor to find the
one(s) that don't cause the light to come on. Since the ABS module has no
speed input besides the wheel sensors, if only a bad sensor is connected the
module can't tell the car is moving and thus doesn't fault on missing speed
signals from the other wheels. Once a bad speed sensor is found, if a new
sensor still doesn't work, there could be a wiring fault in that circuit or a
bad input channel in the ABS unit.

[E30Gus]

Another way to test the sensors is to measure the resistance of all of them individually to find the one that is way off from the others. Don't know if it's the correct way but it worked for me once.