ABS in 93 Classic Gone Whacko ??? / ABS problems / ABS explained

[Darin Dux]

"Mohammad J. Baig" wrote:
> My 93's ABS engages when it isnt supposed to.  Ill be
> cruising down the road and Ill try to come to a smooth
> stop, and all of a sudden....the pedal pulsates and
> you can hear the ABS motor running.  ITs gotten so bad
> that sometimes the motor will start to run when my
> foot is nowhere near the brake pedal.  Another thing i
> have noticed is that when I put the car into first and
> get going the motor will turn for a second or two, and
> sometimes the ABS light will come on.  This specific
> problem happens when I have just started the car.

This very much sounds like the ABS motor relay located under the plastic
cover right beside the ABS actuator.  Pull the cover and then remove the
relay.  This will disable the system for now and keep the motor from
burning itself out.  Does the motor ever run with the car shut off?
That's a sure sign of a faulty motor relay.  Replace with a new relay
(or one from the salvage yard) to see if this helps.  Since it's an
intermittent problem, you can check the relay with a multimeter but it
probably won't show any problems.

> Perhaps one of the sensors on the wheels that detect
> motion (or lack there of) have gone bad.  Where are
> the sensors located BTW.  IIRC this problem started
> when I had my clutch done and the axle seals replaced.

It could be one of the wheel sensors but if this is the case the motor
would only run when you had the brake depressed, even slightly.  Your
symptoms sounded like this until you said that it happens even when you
put the car in gear, I'm assuming without the brake pedal depressed.
The system should only function when the brake _light_ circuit is
energized.  That's where the system gets its power and signal to arm.

FWIW, the most common ABS problems (in order) are 1) faulty wheel sensor
and 2) faulty motor relay.  If one (or more) of the wheel sensors go
bad, the computer will not read the wheel speed properly and will
deactivate the system and turn on the ABS warning light.  If a wheel
sensor is intermittently faulty, the computer will think it's reading
the proper wheel speed and not trigger a fault, but when you press the
brake pedal (even slightly) the ABS system may kick in because the
faulty sensor is sending incorrect wheel speed information to the
computer.  If the relay goes bad, the ABS motor may run all the time,
some of the time, intermittently, or not at all.  If the relay doesn't
work at all, the self-diagnosis procedure the computer goes through when
you just begin to move the car will detect no motor function and trigger
the ABS light and disable the system.

> Lastly, is there is a fuse I can pull to completly
> disable ABS temporarily ?  If so which one is it ?  I
> dont have the owners manual.

You can pull the fuse for the ABS by the battery, or pull the relay as
mentioned previously.

Hope this helps,
Darin