Anti-Lock Warning Light
I am a new 928 owner ('88 S4 Auto) and an even newer subscriber to this list. When I purchased my 928, the anti-lock dash light was on, now I'm hoping that it's just a matter of replacing the anti-lock relay. I've checked the fuse, and it's good. The brakes locked up on wet pavement, so I know the indicator light isn't faulty. Should I replace the relay in the fuse box, or should I "rush the car to my nearest Porsche dealer" like my owner's manual says. The owner's manual also says that only a dealer should replace the relays, is this true? It looks like its just an easy "unplug the old, plug in the new" type deal.
I had the same problem when I bought my '85 928S Euro with the ABS light always on. My fuse was also good and the only problem turned out to be the relay , which I removed and replaced myself. All power was off of course with keys removed from ignition when I replaced the relay. The ABS brakes work great now. As I remember, the relay was unique for the ABS and was very expensive. Check with http://www.928GT.com or http://www.928intl.com for prices, etc.
1985 928S Euro Meteormetallic/black all leather
After much investigation and actually having the car sitting on jackstands with all the tires removed, the discovery was made that the ABS sensor wire had somehow corroded from the inside. Through the process of elimination, a continuity check was performed on what I thought the most likely candidate would be. This was done by bridging one end to itself, and checking continuity on the other end with a meter. While wiggling the connector on the suspension side I suspected the wiring inside had broken or was otherwise bad somehow. So....taking the plunge, I cut the wire at the point where it mates to the connector, and indeed it was very corroded. The same can occur to the brake wear sensor connectors, I've been told.
I had the same problem. The diagnostic equipment showed that my passenger side ABS sensors were burned out. These were replaced, and still no ABS, and the dash light was still on. My dealer then called Porsche, who sent a new ABS unit to test the system. With the new unit installed, the light was still on and the ABS still didn't work. The shop was then able to trace two shorts in a portion of the ABS wiring harness. The shop did not charge me for any of their time or costs in having Porsche ship in the new ABS unit (which was swapped back out for my original unit since mine was working fine), or hunting for the shorts in the system.
They did replace the passenger side sensors, and the ABS harness. The harness is listed as part # 928-612-403-00 on my invoice, and the cost was $125.92.
Hope this is of some assistance.
'88 S4 Auto
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