wheel sensors

[Nobby.bar]

Hi, Anyone come across this problem please, first of all let me apologize for the longevity of this post but I'll try to be as brief as possible.

First of all I got an intermittent fault warning on my 2003 2.5 petrol S-type saying "ABS/DSC. fault" closer inspection with an OBD reader disclosed that the left hand rear wheel sensor/wiring was at fault (C 1175). I duly replaced the wheel sensor, cleared the fault and thought that was that, after only a few miles/days the fault re-occurred. I then stupidly without testing the old sensor repeated the above thinking I must have got a dodgy sensor. Again the fault cleared, but shortly after returned.

Now being a retired engineer I took a deep breath sat down and then the logic kicked in. I tested the old sensor which was found to be OK, ah! must be a wiring fault. I set to task and traced the wiring step by step from the rear sensor connector right through to the ABS unit. I had continuity from connector to connector but none at the ABS unit, so I thought it must be a broken wire from the last connector to the ABS unit. I painstakingly traced along the pair of wires (they run from the passenger foot well down the inside of the wing across the front  behind the front valance, which all need removing for access), all the way back to the ABS unit and it was there that the problem showed its self. the wires from left sensor were connected to the opposite sides pins and visa versa. Now this is a factory wired connector with some 47 pins in it that can't be removed.I checked and replaced the RIGHT hand wheel sensor and the fault was cleared for good.

Now this is where the real problem arises, in skid situation the ECU/ABS/DSC unit will read a stationary/locked wheel and will apply and/or release the brake on the wrong wheel which could have dire consequences!

Any input anyone. There could be hundreds if not thousands of cars out there with this problem. P.S. I've attached the wiring diagram for clarity.

Perplexed Nobby.

 

s-type wiring.pdf