It is certainly unrelated to the LH relay switching (it has no functional interconnection) though that sounds weird - the LH when off is an unlikely source of much leakage...

Alan

 

Hi Joe

By the way, those rear sensors are an ABSOLUTE PIG to remove for cleaning...I only ever managed to get one of mine out before I did what I said earlier....so test at abs unit FIRST.....lol

All the best Brett

 

Hi Brett,

I can imagine, after seeing the photos - removing the rotors and calipers just to get to the sensors, whew, that may be out of my league.

But first things first - I would like to eliminate the relay as a possible suspect. If I had a known, good relay, then I could just swap them out and find out quickly if that is the problem.

Thanks,
Joe

 

It has been a while but I think you can get at them without removing anything. You will need a hex socket hit them with some Blaster and wiggle out.

Test it first:
Chk between pins on Abs unit you should read 800-1800 ohms
4/6
21/23
8/9
24/26

You can use your meter to check for on and off while rotating each wheel.

 

Think removing the brakes makes it easier to get a picture.
Don't remember removing any parts to get the sensors out.

 

Both abs wiring harnesses on my 'S4 are toast on the front. My brakes have the exact same symptoms as yours. I tried to do a fast temp cluge fix on the drivers side which had obvious signs of damage, but it didn't work, so I'll be replacing the harness on both sides

Here's a pic of the right front side. Notice the worn protective sheathing.

You can follow this wiring to where it comes through the inner fender and you may see more worn sheathing on the harness in the engine bay.



This pic shows the white barrel connector in the lower left, this is part of the abs harness. The white barrel connector has a black cover on it, which is also visible, so that is what you would actually look for. Check the wires leading to and from for damage.

 

Only need to remove wheels to get sensors out. Rotor in my pic was off for a different reason.

As well as checking resistance at the ABS ECU, you should start by disconnecting the barrel connector at the wheels and check continuity there reconnect, then at the barrel connector in the spare wheel well, reconnect, then at the connectors under the hood, and finally at the ECU plug. This way identifies a sensor fault first, if none it then identifies if the fault is in the wiring and in which part of the wiring.

 

Hi to all.

I have the same problem in my 928s.

When I start driving the ABS light doesn't turn on but the brake pedal feels rare and hard, like the ABS system was working all the time. Few yards later the pedal turns normal and the ABS light comes.
I think I have some sensors bad and I have to replace them, but I want to know If there's any way to turn off the ABS system until do the replacement.

I have located the ABS sensors but I couldn't locate the wires.

Thank you