Citroen XM Forum

As dieselman says the rear left resistance value is failing the self test.
If the sensor is good resistance you have a defective wire connection on those wires.
Not made solder connections have you as they often look good but can be crap electrically.
The Bendix ABS only checks the sensor resistance once at start up.
After this the resistance values are ignored.
The Bendix does not treat the rear brakes separately but as a single item.
So the ABS releases them both or applies the rear brakes together.
The ABS ECU may get two separate rear sensors waveforms but it only sends one signal to a single ABS valve.
It is possible that it is seeing the missing sensor signal as a permanently locked wheel so the rear brakes are continuously released while braking.
XM rear brakes do so little that you would never notice the brake reduction unless you got the car on a sheet of ice.

John

Thanks John, I am out of my league here really. No I haven't soldered anything. (I did solder the front one some time ago but that reads perfectly fine) and had been working until this week.

If I put a temporary wire set from the plug from pin 15 and 32 to the sensor, should it work with the wrong sensor? I don't really think it would since the 'new' sensor is different resistance.
I don't particularly like to drive abroad with a constantly braking rear wheel or two so I now think I'd take out the fuse? I find it impossible to source another sensor so far.
I've even asked an ABS sensor manufacturer for any info on any sensor with 2200-3200 Ohm resistance, so maybe it could be adapted one way or the other.

Thanks for your reply!

Is there any resistance reading at the sensor plug for the failed one.
This will tell you if the fault is in the sensor and its lead or in the wiring.
Your ECU will accept mixed high resistance sensors (2200-3200) and the more standard (1000-1300) ones.
XM Bendix is the only one to do this.

John

The failed one is in bits I'm afraid see pic. But I will be able to do a 'wire check' (measure resistance between the plug numbered 15 and 32 and the other ends underneath the car and will do this tomorrow. That will give a clear answer to your question. If '15 and 32 are correct on the plug, that is.

I did read some where else about the ECU accepting mixed high resistance sensors but I am not aware if the warning light should go out or not.

Thanks again!

Yes the light should go out if the ECU sees any mixture of in spec sensor resistances.
From tomorrow I am now no longer confined to home so should be able to go over and search the unit for Bendix sensors.

If you PM me an address I will post you either the sensor if I find one or else a 1200 Ohm resistor with instructions on how to use it.
The resistor will replace a sensor and fool the start up test.
That would tell you if that missing sensor is the reason the light is staying on.
Using a resistor will not fool the running test for long as that would always find no signal from that sensor.
If the ECU sees no signal on 40 successive running tests it is supposed to switch out the ABS and keep the warning light on.

John

Wow, this is getting complex, interesting, and worrying!

Jaap, to answer your unrelated question, Turby d was built on the 12 April 1995.

I just drove the Diesel to the Limousin in France from the west of Ireland, 1100 miles or more, ll have to check.. She did 40 MPG doing not too slow speeds around 85 kph and fully laden with tools and stuff. Less so on steeper hills but who cares.

Going through the busy UK I saw no XM's or DS 5's or anything interesting. So far encountered 1 DS 5 and 2 XM's . So up to now I cannot agree the DS 5 is very popular??

Not too bad XM wise, so far

That's a fair old trip Jaap Your XM is doing you proud!

No, it's so rare to see an XM in the UK these days. I've only ever seen one whilst out and about...

I see more BXs...

I saw one in Tilbury Friday morning as I was leaving it was a LHD from Madrid in Spain a base model as it didn't have the left hand display and it simply said TD on the front wings.

Norman

At least it had the right engine.