A dirty connection at the ECU seems to be a very common cause - and the easiest to fix.
Electronic diagnostics can't find WHERE a fault is, only WHAT it is - so a dirty connection somewhere between the guts of the ABS ECU and a wheel sensor will show up as a faulty sensor - which is basically what the light is telling you.
The 'professional' approach is to attach a Lexia or equivalent, read the fault code, change the 'offending' sensor (hopefully cleaning the connector at the same time) and a quick road road test - that'll be a couple of hundred quid! (say £40 'computer' diagnosis, £120 for a sensor, plus an hour or so labour). This may cure the fault. If not, only then clean the contacts at the ECU (10 minutes).
The sensible, cheap (unprofitable), method is to start by cleaning the contacts of the multi-plug (and socket) at the ECU in front of the LHM reservoir.
2012 Subaru Forester - capable but no magic carpet
2011 Grand C4 Picasso VTR+ 1.6HDi - not missed!
1995 Xantia Estate SX 1.9TD in Vert Vega "The Green Lady" - sadly missed
1998 Xantia 2.1 VXD Estate in Mauritius Blue - R.I.P. (terminal tin-worm)
I would suggest most likely to be a sensor I'm afraid.
I had to replace one on my '98 Xantia a couple of years ago, the only fortunate thing was that it was the front nearside that had failed.
You can disconnect the main connector at the ABS ECU and check whether the sensor has gone open circuit with a multimeter. I'm sure there is a post somewhere with the correct pins to test.
If it's a rear sensor than best of luck!!
Mark
Rear sensors aren't that bad a job Linky Link Link
The rough testing info on that thread will tell you which part of the circuit is having trouble. It's then a case of retesting at the relevant road wheel to see if its the sensor/cable or the long coax cable that runs from the connector to the ABS block.
EDIT: I have a funny feeling that I'm letting the side down when it comes to my spelling of 'co axle'.
EDIT2: Spelling changed
Last edited by red_dwarfers on 22 Oct 2010, 07:36, edited 1 time in total.
A year ago I bought the ABS sensor for my Xantia Mk2 on Ebay for a reasonable price (30 Euro) and what came was looking like the original one, just without the Citroen logo on the plastic bag.
Series 1 and Series Two systems are different! The sensors are quite different too.... S1's having a longer, metal covered body, were as S2 sensors are shorter and all plastic.
Series Two used an updated Tevis 20 system, with different, smaller sensors.. which I dont think can be used on Series 1 cars...
The Abs ECU harness is also different...
Paul
Sharing a pug 207 1.6 hdi Sw 16v.
M reg Xm 2.1 td auto exclusive S2 269k and rising
L reg XM V6 12v SEi auto .. Light project