abs

[marco1]

hello, ive a cit xantia 8 years old been very good but last night abs orange light came on went off a coule of runs but seems to be on all the time now ..any idears ..whats the most common fault ..is it a sensor as i belive it might be? dont want to spend citroen garage money on it whats to check first thanks for any advise bye for now...[:)]

[handyman]

Hi Marco, it is worth checking to see if it is the abs ecu as this involves a very simple test.
When you turn on the ignition, does the ABS light flicker at least two or three times? It is very faint so you have to be observant. If it does, the chances are that the ABS ecu is alright and that the fault lies elsewhere.
Next things worth checking are deposits on the commutators on the hubs next to the ABS sensors. A build up of dirt, mud, etc can be the cause, even carbon dust from a leaky exhaust on the two rear units. If dirty, clean up. Check the sensors for any build up of particles, as the magnets attract ferrous particles. Then check the connectors and sheilding on the cables.
If this is all in good order, chances are that you have a duff sensor.
If you want a difinitive answer, buy a diagnostic tool, as this will give you the interegator and pulsed responses and identify which part of the circuit is faulty.

[citronut]

usuly its one of the sensor wires breaking down as they go across from the car body to the hubs,so the wire is flexed all the time the susp is moving,normaly you wont see the break as the outter sleave usuly stayes intact,most of the time it seems to be the rear one as the wire is flexed right where the rear arm pivots,if you can unplug the conectors which are on top of the rear subframe you will find the plugs if you follow the wire from the hub,then you can test them with a meter,the rear plugs are very hard to get to
regards malcolm

[jeremy]

I'd look at the sensors first - as citronut suggests unplug each in turn and measure the resistance. Chances are that one will not read.
jeremy