[V8] Intermittent ABS light and diff locking up

[urq]

Methinks you are thinking airbag, not ABS.  The diagnostic tool for the ABS
installs in line with the ABS brain box ... I'm not aware of any aftermarket
tools for ABS troubleshooting ... bet even aftermarket it would be
expensive.  

In your original post you indicate that the sensors are all pushed in, that
would have been where I'd start.  Since you see impact on both ABS and diff
lock, it makes it clear to be a problem with the signals coming from the
sensors.  Re-check how well the sensors are inserted and look at the ribs
(splines) on the outside of the outer CV joints.  

Good luck!
Steve Buchholz

-----Original Message-----

As long as the crud in the teeth is not magnetic (not iron) you should  
be fine.  The clearance from the teeth to sensor makes a difference  
though.

As for the hit or miss debug method, the ABS system has a connector  
for the VAG-COM type tool. If the system knows enough to turn on a  
light, it should be able to tell you why.
The connector is behind the driver side console cover - near where the  
ABS module itself is located, and where the backup power reserve  
connector is located.

Dave

On Sep 13, 2009, at 7:11 PM, Mark Kalbskopf wrote:

> Whenever I've looked at the ABS teeth, they just seem to have the
> usual rough, dusty, slightly rusty surface, but never any major crud
> or anything.
> What I really need is a magical read-out of the signals coming from
> all 4 wheels while I'm driving.
> Otherwise it's a bit of a hit & miss operation, where I replace each
> sensor in turn until the problem goes away.
>
> Mark.
>
>
> On Sep 13, 2009, at 4:11 PM, qshipq at aol.com wrote:
>
>> I've cleaned many ABS teeth, and this could definitely be the
>> problem.  On the fronts, you can pull the driveshaft out of the hub
>> enough to clean it without major dis-assembly.  I really doubt trans
>> codes will help you in any way here.  I put up a pretty nerdy post a
>> several months ago on how the center locking works on the v8, and
>> Tony described it again well.  It appears you have a diff lockup
>> signal sent from the trans ecu, caused by one of your abs sensors
>> out of whack with the others.  Fix the signal, you likely won't have
>> a problem.  As a rule, the trans ecu could care less what the actual
>> ABS sensor values are, it's only looking for the differences in
>> them.  The ABS computer on the other hand, is looking for actual
>> value *and* differences between them.
>>
>> HTH and my .02
>>
>> Scott J
>> 92 v8 4.2 ABT chipped