Me Again! Abs On The Blink

Hi guys
I put new discs on the front today now the flaming ABS has packed up.The warning light comes on when starting then flickers and stays on.I can't see any obvious problems in the disc area ,I wondered where I should look next?

Thanks for any help

Hi Bosscat,

The easiest and quickest test is to check the circuit resistance for each of the sensors one by one from the ecu plug. You are looking for 1100 ohms or thereabouts. Search for ABS with the search function an you'll find there's a list of pin numbers on here somewhere.

One thing to watch out for. I struggled for a while with the ABS light on periodically on my 2.5. I checked all the resistances and they were fine. I didn't check earth leakage. I wish I had. When I eventually found the problem I had allowed the sensor cable for one of the front wheels to sag so that it was rubbing on the driveshaft. The rubbing eventually wore through the sheath and then the cable. During the time when the cable was being worn away the driveshaft being metal completed the circuit. Thats why a continuity test from the ecu plug showed everything was healthy. Hmmm... never mind. Another lesson learned.

Cheers

noz

Silly question really, but how do I identify the ABS ECU is it in the black box on the passengers inner wing and if so what does it look like?

Hi Bosscat

It would help to know the ORG Number (build day) from your front passenger door pillar. From ORG 6810 onwards the make and type of ABS changed and the ABS ECU was built into the ABS valve block that is positioned down below the battery in the engine bay. There was a further change in ABS type a year or so later. Registration letter is not a good guide as many XM's took a year or so to get sold and registered.

Regards

XMexc

Thanks XMexc

The No. on the door pillar in yellow paint is CJ 7889.
appreciate the help.

bosscat

There may be some cofusion here. The ABS ECU to which the original enquiry refers may be the unit located beside the other ECU s in the plastic box in the engine bay on top of the RH wheel arch. This is the only ECU in that box which has two multiplg terminals.

Hi Bosscat

Thanks for the ORG No. It is important to sort out what brake/ABS system is fitted for the advice to be relevant to your car. I will list out all the Mk2 options I know about as these items may well be useful to others.
Unfortunately Citroen changed the brake/ABS system fitted at least 3 times during the Mk2 production years.
Only the early Mk2's, the 94 and some of 95 model year cars had a separate ABS ECU in the engine compartment black box. It is only these cars and also all Mk1's that you can do the tests that Noz suggests as they have a Third (Large single plug ECU painted black and marked Bendix) in the engine compartment black box as well as the suspension and engine ECU's. From ORG 6810 Citroen fitted Teves ABS to all XM's and the brake/ABS ECU was incorporated into the ABS hydraulic drive block down under the battery box. This makes the fault finding on the ABS much more difficult but in my experience the Teves system is also much more reliable than the one it replaced. After about 18 months further production at ORG 7483 Citroen changed back to a Bendix system but using different brake calipers as well as a new type of ABS. I have just checked the one of my 2.5's (ORG 7693) that has this new system and like the Teves there is no ABS ECU in the Engine compartment black box. It is virtually certain that your car has this latter system. I have not had any problems with it and have not seen any reports from other club members about faults or working on it other that pad/disk replacement.
You could look for ABS connector plugs in the back of the front wheel arches and if you find any try cleaning then remaking the connections. Not having worked on it I cannot be sure what connections this latest system has.
You could get the fault codes read on your XM as this should at least tell you which part of the system is suspect.
Sorry not to be more help.

Regards

XMexc

This post has been edited by xmexclusive on April 20, 2007 06:29 pm