Flahawkfan

Hi everyone - Need a little help regarding ABS brakes.

My '91 928 S4 is being difficult. About a month ago I started getting two errors after I would go about 10 feet. The first one is ABS off and then once that one would clear, I would get a Differential Control off error. This error would also clear, but the ABS light would remain on.

I have followed the manual and replaced two parts:

The first being the ABS relay part number 928.615.124.01

The second being the rear speed sensor part number 928.606.402.01

After these two changes have been done I still get the same errors.

So my question is where should I go next?

Any help/advice would be greatly appreciated.

Thanks in advance.


Gary

Jfrahm

If you move a bit and then get an ABS code, it's usually a wheel sensor. You can test them with a DMM, check out this thread:

https://rennlist.com/forums/showthre...threadid=80557

Hopefully the 91 ABS brain and cable pinout is the same as my 87.

My ABS is still down, I'm looking for a known-good ABS relay, do you have one you would like to sell?

-Joel.

Flahawkfan

Joel,

Thanks for the direction - I will try the wheel sensors next - Unfortunately I don't have a relay that I can sell.
Sorry I couldn't help.

Gary

MikeN

Don't know for sure, but I would look at the back two ABS sensors first......probably the cause of both your problems......as the PSD system
(Diff Control) might use input from the ABS sensors for part of it's control.

Can anybody confirm if the PSD system uses any input from the ABS sensors, or does it have it's own sensors? Don't know this one!

Jim bailey - 928 International

There are THREE ABS relays one on the main board the other two mounted on top of the ABS unit in the left front fender . to access you must remove the splash shield and then the plastic cover to see the other two relays . Part # 928 618 930 01 and 928 618 931 02 . The PSD limit slip gets the wheel speed information from the same ABS sensors but only uses input from the rear wheels .

Jwrightmcps

Hi…

In my workshop manual it stats:

“The lock control assembly is located on an additional PCB in the ABS control unit. This PSD/ABS control unit has 55 pins; Previous ABS control unit versions had 35 pins."

So that means that the problem could be PSD or ABS related, Hmmmm.... I would feel better myself just testing the system with the 55-pin ABS tool instead of just replacing parts in the dark….

Let me know if you need more info on this unit…..

-J

Blown Beast

Just a thought....My ABS and PSD were doing the exact same thing and I found it to be a air bubble in my fluid line between the resavior and the rear-end.
Check your PSD fulid level in the left rear quarter pannel and then bleed the line.
This fixed the fault lights I was getting
Just my .02

Flahawkfan

Gentlemen, Thank you for all your help regarding my ABS problem - It was finally fixed this week. I changed the ABS speed sensor, and 3 abs relays (92861512401,92861893001,92861893102) and still didn't get the problem fixed. I tested the wire harness from the two rear wheels and was getting no current from the right rear sensor. The harness appeared to be bad. I ran a jumper wire from the sensor to the start of the harness which solved my problem. I've had the car running for two days now and I am falling back in love with it. Thanks for all your help!

Gary
91 928 S4