ABS Wheel sensor signal generator

[Roger Heflin]

On Sat, 3 Apr 1999, Chris Moore wrote:

> Hi Shannen,
>   I have the GM manuals for the 1995 Seville.  It is very nice.  It 
> still does not have the info that I need in it.  The wheel sensor is 
> different than most.  It is internal in the wheel bearing and I cannot 
> count the teeth.  How else can I get this signal?  Dealers probably 
> won't have a clue.  They usually never do.  Especially when I tell them 
> what I am doing.  Is there some how I can use the bearing and just spin 
> it by hand to get a signal and do some math to make sure I can make a 
> generator that is set over the 18 mile/hour mark?
> Thanks
> 
> Chris Moore
> 
> 
You might read the manual more carefully, I have found they have alot
of info like this but nothing is organized in such a way that it can
be found easily. 

Here is what my 93 Z28 abs maunaul says:
The signal from the front wheel sensor is an AC voltage witha a
frequency proportional to the speed of the wheel.  he magnitude of the
voltage increases with increasing speed.  The front wheel ones in the
Z28 are built nto the hub.

It goes on sto say the rear sensor has 106 teeth.

>From everything that it seems to say, you should be able to spin the
hub by hand and get a signal out, and if you had a o-scope you could
probably determine how many teeth it had from the signal going out
and the rpm you were turrning it at.  You could also hook up the hub
and sensor to the computer, and find someone with a toool that can
read the ABSD c omputer, and spin the hub and see what speed the abs
computer thinks the car is going, and also find the frequency of the
signal, and see what will trick the computer correctly.

The 93 Z28 usees a GM ABS computer, I know some other GM cars were
supposed to use a Bosch computer.

Also from the codes I can see it may (the abs computer) also get
unhappy if it does not detect the abs hardware (modulators) being
there.  It also says that it stores the codes in non-voliatel ram so
the codes that are set will not be reset by pulling the battery cable.

You may want to hook up the abs light just so you can see if you have
successfully tricked the abs computer.  I don't know what code readers
will deal with the abs computer, but if you found a mechanic that had
one that wwould probably help.

			Roger
			93 Z28