Xantia ABS

blueboy2001 · Post by **blueboy2001** » 16 Jun 2003, 15:44

The ABS on my Xantia has never worked since I got it, at first I didn't think it was fitted but later found the ECU and the valve block so it obviously is.
The dash warning light functions as it should and doesn't illuminate when driving, so I have no problems getting an MOT.
The brakes are fine as they are really, but I would be interested to know why the ABS doesn't cut in at all.
I know the ECU's are a bit iffy on these and tend to fail but I would have thought if it had the dash light would be on. Any ideas?

AndersDK · Post by **AndersDK** » 16 Jun 2003, 16:10

BB-
Could it simply be a blown fuse ?
Haynes is no help - no schematic on the ABS system.

jeremy · Post by **jeremy** » 16 Jun 2003, 16:38

When you say the warning light is functioning correctly I presume you mean it is coming on for a few seconds at startup and then going out and staying out.
I think the warning light is supposed to come on if there is a failure of the fuse as there are 2 supplies and since the checking is fairly comprehensive and the warning lights cant be put out without bulb removal I don't think that is the problem.
How are you testing the system? I say this as I have it on my TD and have only had it come on a couple of times. I have driven the car without it for some time and can honestly say that I didn't miss it as the basic system is sogood. When I first got it going I did get a couple of pulses out of it in a carpark with a loose surface, and also got it to work in snow - just so that I would know what happened.
have a look at this link
http://www.bba-reman.com/index.htm
and this one
http://www.carelect.demon.co.uk/
The second one offers a reasonably priced diagnostic service as well as repairs.
jeremy

blueboy2001 · Post by **blueboy2001** » 16 Jun 2003, 17:10

I've just checked the fuses and they're ok. Are there any test I can perform on the relay, I think its got to be either that or the ECU.
As for testing, I am standing on the brake pedal and the front wheels are locking up. I'm not particularly bothered by it, it does take a real kick of the pedal to get the wheels to lock up.
The light does indeed come on for 2 seconds then go off at startup. I've looked at BBA and the other site, as well as all the other ABS related posts on here and they all seem to state the problem as being the ABS light being on. As mine isn't I suppose that suggests the ECU is ok. Maybe the valve block has had it?

jeremy · Post by **jeremy** » 16 Jun 2003, 20:56

yes my understanding is that the light extinguishing is a sign that all the electrical bits are ok. As a matter of interest i would have said mine (Teves? system) stayed on a bit longer than that and gives a flicker before it goes out.
I believe the units fitted around '94 are very troublesome and well known for failure.
The only bit that isn't checked on startup is the brake light switch which activates the whole thing when its needed. It could be worth checking this circuit carefully. Mechanical/hydraulic faults seem unlikely as no-one has ever mentioned them on here, and in any event the valve block has 3 sections (2 front, 1 rear on BX) and its unlikely all would fail together.
jeremy

cheesey · Post by **cheesey** » 17 Jun 2003, 00:05

Most systems are set not to work at speeds up to 5 mph to 10mph. so to test you may need to boot it a bit. Also I had problems when I rotated a wheel with the engine on and car jacked up. The ECU noted the other wheels not moving and conclued that something was wrong.

Dave Burns · Post by **Dave Burns** » 17 Jun 2003, 04:23

Check that the ABS light does not extinguish allways in time with the oil light or any other light, if it does it could have been tampered with.
Do you lose directional control during heavy breaking or can you still steer.
Dave

blueboy2001 · Post by **blueboy2001** » 17 Jun 2003, 05:55

The thought of a little bit of tampering to get the car through an MOT had crossed my mind. I don't think it times exactly with any of the other lights though, I will check properly tomorrow. If I remove the ECU plug should the light come on? If so I'll try that and see if it affects the lamp operation to ensure the lamp is actually connected to the ABS system and not something else.

blueboy2001 · Post by **blueboy2001** » 17 Jun 2003, 22:46

Had another look today - disconnecting the ECU leaves the light on constantly, so it would appear thats ok. Do the wheel sensors connect up anywhere into the ECU loom with multiplugs? I have a loose multiplug in the vicinity of the airbox which I cannot seem to find where it connects to. If the wheel sensors had been removed from the ECU, would that mean the light would stay off?

Homer · Post by **Homer** » 18 Jun 2003, 02:29

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by blueboy2001</i>

As for testing, I am standing on the brake pedal and the front wheels are locking up. I'm not particularly bothered by it, it does take a real kick of the pedal to get the wheels to lock up.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
At what kind of speed?
The ABS system doesn't work at all at low speeds (10mph ish) I know this because I've almost come a cropper a few times when our street is icy.
I would test it in a damp road, with nobody else around and from at least 30mph.
At one time I had a '94 Xantia with ABS and a BX without. After driving the Xantia for a fortnight I locked up the BX wheels on a dry road. The Xantia ABS ECU failed on me as well and while it wasn't working I had to be very carefull in the wet.
In use you hardly notice the Xantia ABS anyway. It doesn't give the same pumping sensation through the pedal that other cars suffer from. The only time I have had that was when one front wheel was on mud and the other on tarmac.

wheeler · Post by **wheeler** » 18 Jun 2003, 03:52

if a wheel sensor is disconected the light will stay on.

pwatson · Post by **pwatson** » 18 Jun 2003, 04:47

Have you tried the diagnostic tests as outlined on this webpage?
http://www.woollard.com.btinternet.co.u ... ad.htm#ABS
it's for the BX but it's basically the same system.

blueboy2001 · Post by **blueboy2001** » 18 Jun 2003, 05:45

I went out earlier this evening and braked sharply from just under 60MPH. The wheels must of locked up because by the time I'd come to standstill I was surrounded by a cloud of tyre smoke and there was a bad screech, I think it was the rears that had locked up actually - I am aware that the rear discs are absolutely shot and I intend to change them at the weekend.
I cannot even provoke the ABS in the yard at work, its full of loose stone and the C5 ABS goes mad whenever you brake hard on it.
Next I will find a multimeter and check the wiring. Can anyone tell me how to test the ABS relay using a meter?

alexx · Post by **alexx** » 18 Jun 2003, 12:08

Homer, I still don't have a Xantia (didn't find a proper one yet), but on several Xantias I've driven, pulsing on the pedal during ABS in action was like in other cars, just a little less intensive. You can't miss it.
About minimal speed, I don't have info about Xantia, but on ZX, ABS works above 5 km/h.

jeremy · Post by **jeremy** » 18 Jun 2003, 12:59

Have a look at the ABS section of this site - official Citroen instructions - for BX I think.
http://www.rwbsmith.plus.com/citroen2/
Wheel sensors should be picked up by the checking routine as should the rest of the electrics.
As I mentioned above the system is activated when the brakes are applied, as simply monitors itself at other times. It is in fact connected to the brake light circuit and this is not monitored as the tests are carried out normally with the brake light switch open. If there is a problem with this circuit then the monitoring will be normal but the system simply will not work. I think the switch is connected to terminal 12 on the ECU. From my diagram there are no plugs etc in between the stop light switch and the ECU. It could be a wire has simply dropped off the pedal switch.
There is a full wiring diagram in Haynes 95 edition page 429. If you need it I can send you a copy but will need your e-mail address.
Jeremy