[No EFI] ABS Help Needed

[Rich Vandervoort]

This has the symptoms of a wheel speed problem.  This ECU should store the 
codes, but I don't know what the protocol is.  While the wheel speed sensor 
may be in good shape electrically there may be other problems such as; the 
gap between the sensor and reluctor ring, contamination of the reluctor ring 
with metalic particles, bad wheel bearing causing sensor gap variation.  
Fortunately the ABS system is sensing a failure and you should be able to 
use this information to help diagnose your problem.

Rich V.

Date: Fri, 28 Apr 2000 11:03:35 -0400
From: "Mike Turner/ENGR/HQ/KEMET/US" <MikeTurner at kemet.com>
Subject: [No EFI] ABS Help Needed

Where might one find any information on troubleshooting, communicating
with, replacing, etc. an ABS unit for a late 86 (ie 87) Corvette?

Ours has developed a couple symptoms. The first occurs just after mild
brake application. On release of the pedal, the abs kicks in and the pedal
starts vibrating for a short period. The other symptom is the ABS light
coming on sometimes after this event but not always. ABS action during and
after hard braking looks and feels normal.

I have considered a complete brake line flush including the lines to the
abs unit. Removal and replacement of the abs unit looks non-trivial to my
untrained eye. My local vette experts indicate fluid contamination should
not cause this symptom. A sticking pad or caliper could fool the abs (ok
the wheel may actually be locked up and abs is just doing its job but seat
of the pants says no wheels are locked since car is slowly rolling). Ditto
a flaky wheel sensor.

Additional info:
Calipers replaced a few months ago. Symptoms did not immediately appear
after replacement.
Brake pads are hawk autocrossers which squeal impressively.
Rotors are stock.


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