ABS Help

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CITROEN-SUCKER
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ABS Help

Post by CITROEN-SUCKER »

Hi just had the car in for its MOT today as expected it failed but the one thats being a pain is the ABS i thought it was the front sensor so replaced both of the front ones no luck noe light is on all the time never goes out at all help
Thanks
J.J.
ps the car is a Xantia 1.9 TD VSX
RichardW
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Post by RichardW »

Do a search on here for Xantia ABS - I think someone has posted the pin out for the connector so you can test the sensors (should be around 1k ohm each). Unfortunately Xantia ABS ECUs are not the most robust items on the planet and this may well be the cause of your troubles. My mate got a 2nd hand one for his for about £80.
BrianM
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Post by BrianM »

If, when you switch on the car the ABS light filckers this apparently shows the ABS ECU has completed its self test successfully. If the ECU has failed its possible to get the unit repaired.
jeremy
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Post by jeremy »

have a look at:
http://www.bba-reman.com/index.htm
and
http://www.carelect.demon.co.uk/
Worth checking all fuses used in the ABS as well as testing all sensors for continuity and having a look at all electrical connections on valve blocks etc.
Jeremy
jeremy
David W
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Post by David W »

JJ,
What was the sequence of events surrounding the ABS failure...like has the light been on for ages and did it start by being on and off from day to day?
I can give you all the pin numbers if you can't find them in a search....assuming you want to do a DIY repair.
Do you think your MOT man would have passed the brakes if he hadn't seen the light on??
David
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Post by CITROEN-SUCKER »

Hi just replaced both front sensors today with some from a car i know is ok. All seemed fine turned on engine ABS light did the flicking thing then went out Great? all being fine put rest of car back together went for a short spin within 10 meters the light was back on so stopped car turned off back on and light went out again. Dove a short distance and back on does this mean the back ones might be away? Any quick cheats as the car goes back for a retest on monday
thanks
J.J.
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Post by wheeler »

wire the ABS light to the oil pressure switch [}:)]
CITROEN-SUCKER
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Post by CITROEN-SUCKER »

Think my garage will spot that they seem fairly adept at this also my oil presure light somtimes blinks on and off for about 15secs on startup so that would be to suspect
thanks anyway
jeremy
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Post by jeremy »

I suffered from this problem on my BX and eventually traced it to yet another faulty sensor. I connected each sensor in turn to an audio amplifier and listened to them and eventually found that one was significantly weaker than the others. The fault was that when I had replaced corroded leads I had also replaced a plug/socket on one and had left a whisker of wire which was shorting.
I think you have a defective sensor lead which breaks the circuit when you move the car and the suspension moves and flexes the lead.
Jeremy
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Post by acrowot »

The front sensors are different on the early cars made up to late 1993 I think, there is not a lot of difference, but if you have fitted sensors from the later car onto the earlier car the sensor will be further away from the castelations on the drive shaft, this would produce a weaker output or no output from the sensor, this would give the symptoms you describe. The initial test of the sensor is only to test its resistance if this correct the light will extinguish but when you start to move if the pulses from the sensors are not detected then the light comes back on and ABS is disabled.
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Post by uhn113x »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I suffered from this problem on my BX and eventually traced it to yet another faulty sensor. I connected each sensor in turn to an audio amplifier and listened to them and eventually found that one was significantly weaker than the others. The fault was that when I had replaced corroded leads I had also replaced a plug/socket on one and had left a whisker of wire which was shorting.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Hey, Jeremy, you should have recorded it - the Paxo-driving baseball caps would be queueing up! [}:)][;)]
alan s
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Post by alan s »

How clean are the serrated wheels that the sensors operate on?
I've seen a couple of UK cars that have had the salt syndrome & the rust build up is pretty incredible and I can understand how it creates false readings.
The metal filings on the sensors would nearly have to be a worry too.[B)]
Alan S
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Post by mark_sp »

where are you ?
If you are in the UK and anywhere near Staffordshire I can recommend an independant specialist who charges a very reasonable £15 to diagnose ABS faults. Did mine recently and said it was RH front sensor. He was spot on, recently replaced it and all okay.
Incidentally wasted a bit of time because I first inspected old sensor and cabling. Old sensor had a 2mm crust of oily brakedust cr*p baked on. Cleaned it up and refitted and all was well for a few hours until it rained, then warning light came on. So did the job properly and replaced the sensor and its been okay since.
Mark
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Post by NiSk »

If you are only worried about the MOT for the moment, then your "loaned" sensors will do the trick. When testing the braking system, the rolling road isn't allowed to exceed approx 5 mph, since otherwise the ABS system would start to operate when the maximum braking effect is being measured. So as long as they don't take the car for a spin (and exceed your 10 mph) you'll be OK.
As far as fixing the real problem, do as recommended earlier, check out the resistance of each sensor att the ABS ECU. The problem is often due to cable brake or connector oxidization, not a fault in the sensor itself.
//NiSk
David Goddard
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Post by David Goddard »

Corrosion on the connectors does cause low output from a sensor. Find the connector, clean with contact cleaner and slap on some vaselene should be a long term cure. The sensor output can be measured with a digital multimeter - millivolt range (AC) by connecting a meter to the multipin socket. 10% or even 20% voltage difference on an axle pair seems to be acceptable to the ECU. Front and rear sensors have a big differnce in their outputs.
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