BX ABS problem

Huwbruin · Post by **Huwbruin** » 20 Jan 2004, 19:15

Hi
The ABS warning light on my 1990 BX Gti (8v)is on constantly.
I suspect a sensor or wiring problem. There is no obvious damage to the sensors or visible wiring and I have cleaned the toothed wheels and the sensors and unmade/remade the wiring connections under the rear seat.
I have checked the resistance at the ecu for all of the sensors and obtain readings of about 1030 ohms for each of the front sensors and nil for the rears.
Now I do not pretend to understand electrics but I presume that there should be some resistance in the circuit and the lack of a reading from the rears indicates a problem at that end.
Of course this may be completely wrong.[:I]
All advice will be appreciated.

mbunting · Post by **mbunting** » 20 Jan 2004, 19:17

I would agree with you. Check all the wiring from the rears at each joint. Is it definitely both rears ? There must be a common connection / wiring path somewhere, trace it.
Perhaps the connections were broken during a rear arm bearing replacement weekend ?

Huwbruin · Post by **Huwbruin** » 20 Jan 2004, 19:51

Thanks
I agree it seems strange that both sides are u/s but there seems to be an individual feed to each sensor, unless it is common somewhere in the depths of the loom[:(]

AndersDK · Post by **AndersDK** » 20 Jan 2004, 20:00

The wiring to each wheel sensor is separate - 2 wires (or antenna like cable).
It could well be both rear sensors dodgy - or the cabling is chafed somewhere under the rear seat squab or carpeting.
Another test is crucial : the sensor wiring must not have earth connection. Same goes for the sensor housing.

jeremy · Post by **jeremy** » 21 Jan 2004, 00:52

Has the light just come on or has it been on for a while? On my TD I found I had 3 defective sensors, all suffering from the same problem - corrosion of the screen of the co-ax cable. I was able to repair them by cutting back to good cable and soldering in lengths of flexible co-ax.
If the light has only just come on then I agree that this is unlikely but if its been on for some time then who knows. As a matter of interest when I purchased the car someone metered it and the 2 rear ones had failed. In the 3 or 4 months before I got round to dealing with it one of the front ones had failed as well.
Jeremy

Huwbruin · Post by **Huwbruin** » 22 Jan 2004, 03:24

The light has been on a while. Sounds like it is not so unusual for both rear sensors to be u/s.
I think the car stood idle quite a lot in its recent history so maybe it is a corrosion issue causing them to earth out?
The wiring seems outwardly sound but clearly it could have a hidden problem....
Seems like I'll have to get to grips with my new multimeter!

jeremy · Post by **jeremy** » 22 Jan 2004, 04:31

On my sensors the rubber outer covering had deteriorated and when bent showed cracks. The screens were extensively corroded over a considerable length.
Jeremy