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I went through the same issues with my 05 W12. It ended up being a wiring issue on the 4 wires for the rear ABS sensors. The corrosion started at the ABS connector under the hood. It was slightly covered by the wiring harness protective wrap. After I removed the left front wheel and inner splash shield - I removed the wiring harness at the ABS module - unwrapped the protective covering and found the insulation on the wires for the rear ABS sensors was gone. The corrosion had destroyed only the 4 wires going to the rear ABS sensors. I replaced about 12 inches of wiring for each wire and the problem was gone.
I will find my previous post and post it up for you.
Since it is only the 4 wires for the rear ABS sensors, I would say that the wiring used was probably not up to spec. ALL of the other wiring was perfectly fine. That being said I think it was most likely something getting on the harness and the "not up to spec" wiring insulation failed which then resulted in a short - then an eventual break in the wiring.
There is a coolant line "tee" in that area by the ABS assembly on a W12, I did end up repairing that connection as well shortly after the ABS wiring repair. It is possible that the occasional coolant drip or leak on the wiring could have caused this.
Still odd that only the 4 wires for the rear ABS sensors failed.
Well, with ears glowing from embarassment I can report the case as being solved. By a workshop.
They did what I hesitated to do, look into the seemingly undamaged wiring mash. Ten years and an hot engine as neighbor does wonders to cables. Not.
Now the life is good again, everything in working order.
Lessons learned?
When electical foults appears in connection to wet conditions - the prime suspect is wiring.
The picture is taken into the wheel house from rear facing forwards, the connector to the ABS-module is the bluish thing close to the suspension strut.
So this looks like it might be something for us folks with older cars to keep an eye on. Loom deterioration. What could be done to prevent it or slow it down I wonder? Hope its not something widespread with the wiring insulation as something like this could total the car. Many Merc W140 s-classes from the 90s saw their demise this way.
Replace every cover, shroud and clip whenever servicing the car. Don't park in areas where part of the car could get submerged. Do not drive through deep, standing water.
Last edited by Mister Bally; 02-06-2016 at 09:04 AM.
Accordning to the workshop, this behaviour is quite common in VAG-cars. The insulation will turn to hard and unflexible, same with the wiring inside. They have seen cases where looms has looked like overcooked spaghetti with same snap-factor.
I'm having the same issue with my 2006 a8l. Replaced the front left speed sensor and battery with no success. My abs/esp/parking break faults are intermittent and did first occur in wet conditions. I'm going to look into the abs wiring harness next- thanks
02-21-2015, 12:52 PM
