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Re: Busted ABS sensor

Date: Tue, 29 Jul 1997 00:03:52 -0400 (EDT)
From: johnholt@cybernet.on.ca (John Holt)
Subject: Re: Help...hard brakes

>Hairy green toads from Mars made John Holt say:
>> Initially, when I depress the brake pedal of my 90Q, the pedal 
remains at
>> the top of its stroke, it is very hard to depress and there is 
some text deleted
          >ABS sensor busted/misaligned.
          >BTDT yesterday....
          Great diagnosis, Andrew....
          Press ABS dash button OFF.... problem disappears
          Press ABS dash button ON .... problem reappears
          Now I can safely drive the 90Q .... the one with the working 
          air conditioner after I determine which sensor is out of 
          Thank you
          John Holt
          2 of those 1988 90Qs

If you put an oscilloscope or ac voltmeter across the pins of each 
sensor connector, you can tell which is likely bad.  This is done by 
jacking up one wheel at a time and "kicking" it by a calibrated amount 
to cause it to rotate and reading the sensor voltage.  My wife' car, 
which has an annoying intermittent ABS action when ABS is not 
required, reads two volts p-p on the two front sensors, 4 volts on the 
rr sensor, and 1 (at best) on the lr sensor.  My bet is on the lr 
sensor, which can't get any closer to the cogs it senses.  Your 
voltage will be proportional to the rotation rate generated by your 
kick.  Of course, you could put the car on a lift and get all wheels 
to turn together at a constant rate.

On my 1988 90qs, the rear sensor connectors are under the back seat 
cushon, one each side.  (Two phillips #3 and you are there.)  The 
front sensor connectors are attached to the strut towers in the engine 

***                 ...Kirby    (Kirby A. Smith)                 ***
***                      2 X 1988 90q                            ***
***              ksmith1@mailgw.sanders.lockheed.com             ***
***              [=]   kirby.a.smith@lmco.com                    ***
***  Opinions expressed herein are entirely those of the author. ***