Xantia ABS light....

[SimonT]

For the sensors and as Andrew says it will probabally be one, try this.

Ensure ignition is off.
Unplug the muliti plug from the ABS ECU.
Use an OHM meter to take these readings.

Pins No 15 and 30 = Left hand front sensor

Pins No 1 and 6 = Right hand front sensor

Pins No 19 and 28 = Left hand rear sensor

Pins No 29 and 31 = Right hand rear sensor.

All readings should be 1080 OHMS approx, in reality if you get no reading then the sensor is duff. But it is allways worth cleaning the connections.

If you shine a maglight at the pins you should be able to see the numbers of the pins.

Good Luck
Slim

Done a little drawing of the pinouts too if this helps anyone
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[TehAgent]

er... where is the ABS ECU? anyone got any pictures of the engine bay with it in? also what part do i test and what way round do you connect the red and black Miltie meter connections to the pins or doesn't it matter?

Also anyone got a diagram or photo as to what you have your meter set on?

[jeremy]

The resistance of the sensors is about 1000 ohms - so choose the next largest scale. If you use one of the most sensitive (highest resistance - biggest number) it will probably read anyway - you'll find that your skin conducts quite well - and tracks from a pencil drawn on paper will read as well (and give a resistance which varies in relationship to the line length)

You are testing the sensors which are not connected to anything else - and they are not polarity conscious - so connect as convenient. DO NOT try and meter for resistance on the ECU unless you know what you are doing. The meter measures resistance by feeding a current at 9 volts through the subject and measuring the current and this may damage the ECU. The voltage and current measuring is entirely passive and simply draws a small current from the subject in the case of the voltage setting and is in line with an existing circuit for amps.

[jadonx]

Thanks slim and Simon. Found this site after paying for diagnosis which the mechanic said it was likley to be rh front sensor but could not still discount an ecu fault. Using the diagram, I found the rh front sensor open circuit across pins 1 and 6 on plug. I have obtained a used sensor and fitted, even though I had to adapt slightly to fit as not exactly the same.
All now working fine. I have just recently had the same side cv joint replaced so could of been the cause of failure. Thanks again nice forum!
John.

[Mandrake]

Great to hear that. Yes, it could have been damaged while the CV joint was replaced - the teeth for the sensor are on the outside of the CV joint.

There are also two versions of the sensor based on the model year, with slightly different lengths of the stalk. Sounds like you managed to get it to work though.

Regards,
Simon

[jadonx]

Thanks Simon, I should mention that the sensor might of been damaged by excessive vibration of the badly worn joint prior to the cv joint replacement (the ABS light was on as I took it in for repair).
My vehicle is the 1997 1.9 td desire to which I fitted the slightly different sensor off a car from the same year.
I compared sensor length which when held together looked the same but when I came to fit, I found the senser diameter a touch wide. This was soon sorted with a slight rubbing with abrasive cloth on the plastic body(other was metallic). The holding flange was about 5mm narrower so needed afew 6mm washers on holding stud prior to fixing. Measured resistance at breakers yard and found to be the same as on good LH side sensor- about 1.18k ohms.
I'm very satisfied with repair and thanks to this forum again.

[jeremy]

Unless there was physical damage (which would be apparent on inspection) I think it unlikely that replacing the CV joint damaged the sensor. It could have failed due to water ingress - but its more likely that its lead has failed due to excessive flexing - so its vital to make sure it isn't kinked when the suspension moves.

[jadonx]

Hi Jeremy, as i said - "excessive vibration of the badly worn joint prior to the cv joint replacement ", I don't mean the cause was the actual repair job. I have cut the wires close to the sensor body and still obtain an open circuit and there is no sign of cracks on body either. Looking at other posts I should lookout for spare for LH side as these are the most common failures.

[frenchcarnut]

I have an 'M' reg Xantia diesal and its just failed the mot as the ABS warning light stays on. Now, having read a bit i know that the ECU is a fault in these and my question is whether its worth getting another from a donor car..

What is the probability the the ECU is the likely cause? and if not, waht else could it be?

I had 3 wheel sensors go on mine in 7 years, 2 nr side front, 1 off side front. The last one replaced lasted 4 months. So the garage which took it off my hands would have needed to replace it a 4th time to get back on the road.

[Ross]

I went through all this last MOT (loads of money) and seem to have the same problem this MOT - did the testing and renewed some sender units - even had the ECU repaired but the mistake I made was to renew the units and have the ECU repaired seperately - when I put it all back together it still didnt work and I still had to pay for testing, diagnosis and repair together, with an MOT
Still not convinced the repair was complete and the system working properly but at least I got an MOT cert and that was what I was after.
This time I'm just going to take the whole car in for testing and stick it on the plastic

One thing I did find out tho is that its really easy to access the rear suspension and ABS plugs if you remove the spare wheel and pan first - only one bolt and the access improves drastically - it might seem obvious but I didn't know.

I hate ABS - lol