Xantia 2.0HDi (W reg) 2000 MY - ABS problem

[JohnP]

This problem is definitely doing my head in:
ABS system checked out by local friendly Citroen agent (no faults found)
Rechecked system with multimeter at ABS multi pin connector (everything checked out OK.
Everything seems to work OK except that as I brake and the car comes to a halt the ABS cuts in at the last second just before the car actually comes to a stop (this is under normal braking conditions).
When braking from say 30mph and hitting the brakes hard in an attempt to lock the wheels ABS works perfectly.
Help,Help,Help!!!!!!!!!

[Mandrake]

Hi,

Sounds a lot like the problem I used to have which I described in this thread:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=19316

Does it happen fairly regularly ? If so, as a test just pull out the ABS fuse and see if it still does it. I bet it doesn't.

In that case you DO have an ABS fault, just an intermitant one.

When I had this problem the ABS warning light did NOT come on most times, so the absense of an ABS fault light doesn't guarentee there isn't an ABS problem.

It's highly likely to be an intermitantly faulty cable to one of the sensors which is affected by the cable flexing as the suspension moves.

Unfortunately if the ABS fault codes don't reveal anything it could be very difficult to find. I wasn't able to find and fix mine until it finally started playing up enough to bring the warning light on.

Possible approaches to finding a cranky intermitant problem like this would be:

a) jeremys suggestion of connecting a small speaker to the output of the ABS sensors (one at a time) at the connector to the ABS computer and listening to the sound while driving, listening for unusual changes to the sound that might indicate an intermitant fault.

b) doing an ohm meter test on each sensor from the main ABS computer plug while fully lowering and raising the suspension and (in the case of the front wheels) turning the suspension from lock to lock. You could also try wiggling and tugging on the cable in the wheel arch manually.

The pinouts for the ABS computer are somewhere on this forum...

Regards,
Simon

[Richard Gallagher]

If you can find someone (like me ) with a fault code reader that does 'Datastream' i.e. a profesional diagnostic tool, then you will be able to watch the the actual speed registered on all of the sensors at the same time whilst the car is being driven.

[AndersDK]

John -

How do you know its the ABS cutting in ?
The Xantia brakes system can do weird things like a pulsing brake pedal if the main accumulator sphere is near/flat - which is about right for a 6 years old car.

[JohnP]

Thanks for replies so far.
With regard to your suggestions so far and I am now convinced I have an ABS fault as I have tried driving the car with the ABS multipin disconnected at the ABS unit and the brakes behaved normally with the exception that I can now lock the wheels under heavy braking (ABS light also on).
Unfortunately I need to rectify problem with some urgency as MOT test is only a few weeks away.
Will try your suggestion Mandrake with multimeter and citrobics.
Will let you know the outcome.

[PowerLee]

As long as the ABS light works correctly for the check sequence & the brakes pass the rolling road test then theres nothing to worry about brake wise at MOT time.

Get the MOT done & the investigate the brake / ABS problem further.

[RichardW]

My wifes ZX used to do this - it's much better since we did the clutch and cleaned all the rust / crap out of the ABS rings on the drive shafts while we had them out!