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Subject: How to remove the ABS computer Author: DavidC (moderator) : member since December, 2003 : 12424 posts Posted on: 2005-03-18 14:43:25

I've been trying to diagnose a persistent ABS instrument light in my '86 735i. The problem is that the ABS light illuminates shortly after the car starts moving and stays on after that.

Each ABS sensor has already been removed and cleaned on all four wheels. There is some rust on the teeth in the hubs, particularly in the rear wheels, but no teeth appear to be missing. I'm not sure if I should replace all four sensors or not, but they're somewhat expensive so I haven't done that. I did hook up an AC voltmeter to the sensors and they do appear to generate a voltage that's relative to wheel speed.

I found a replacement ABS computer for $10 at a junkyard so I thought I'd use it to test/replace the one currently in the car. I had hoped that the problem would be an easy fix but, alas, the new ABS computer acts the same as the original one, so I guess one or more of the hubs or sensors are at fault. I don't know how to test the hydro unit.

In any case, this provided a good opportunity to do another BimmerBoard article, so read on to see how easy it is to remove and replace the ABS computer. The only tools you'll need are a philips screwdriver and a 10mm hex socket.

The ABS computer is located on the right side of the dash, above the glovebox. Open the glovebox and remove the screws holding the flexible plastic cover above it. The ABS computer is the rectangular metal box on the right side.


Remove the 10mm hex screw from the front bracket.


The rear bracket of the ABS computer can now slide out of its retaining bracket.


Hold the ABS computer in one hand, then depress the metal clip at the rear edge of the white plastic connector. The metal clip is part of the ABS computer housing. This will release the end of the plastic connector. The front end of the connector has a plastic tab that fits in a slot in the metal housing. Rotate the rear end of the connector away from the metal housing then slide the front end out.


Here's a view of the plastic connector removed from the ABS computer.

David Cecil
Lexington, KY
Titanium silver '01 750iL, 92k miles
Oxford green '97 740iL, 184k miles
Alpine white '92 750iL, 95k miles (for sale)
Charcoal gray '86 735i, 101k miles (for sale)

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