Re: ABS sensor signal

["Scott M." <scottmo@teleport.com>]

Gary,

You want to connect the O-scope across both wires going to
the sensor, these sensors are made up of a permanent magnet
surrounded by a coil of wire. It generates an AC signal
that looks similar to a sine wave. You can disconnect the
front sensors inside the engine compartment and attach the
scope to the two connectors and then spin the tire to see
the signal. I assume the rears have connectors back there
somewhere. 

The amplitude and frequency of the signal will increase
with wheel speed. It might help to get all four wheels off
the ground and spin the wheels with the engine running,
trans in gear. Be careful! Check the signal for any high or
low peaks due to damaged teeth on the CV joints or possible
metal shavings build up on the sensor. If you have a DSO,
then use the roll or scroll mode (very slow time base,
>500ms) to look for abnormal spikes or drop out in the
amplitude with the wheel turning a fairly steady speed. The
important thing is for all four sensor outputs to be fairly
similar in amplitude and frequency with all four wheels
turning the same speed. The distance between the sensor tip
and the CV teeth will change the output amplitude
dramatically. Sometimes it helps to pull the sensors out
and clean off the crud from the tip.

HTH
Scott M.

> List,
> Can someone describe how to hook an oscilloscope to said
sensors?  I
> don't have a clip-on current probe, need a direct
connection.  I'm
> wanting to troubleshoot, and this would seem to be the
easiest way.
> --Gary
> 
> ('86's:5ks&5ktq+'87CGT)