Which pins do I test on the ECU with a multimeter, I read Peter N's post but not sure if his car was a S1 or S2. Mine is a 1994/5 S2 bendix system on a 2.5

I had a perfectly working ABS system until I went abroad during the cold winter & left the XM standing in the driveway for 4 months. When I returned the ABS light stayed on & the matrix message says 'ABS OUT OF USE' I jacked up the front of the car & unpluged the ABS connectors under the wheelarch, one of them was corroded so I scraped it off with a screwdriver & packed it with grease but it hasn't made a difference. Not sure where to find the ones at the rear.
I've done my back in as well so would rather test from the ECU for an open circuit before messing around underneath the car.

On a separate issue I need to get the tracking done on the front as theres uneven wear on the tyres, would any normal tyre place be able to do the tracking like on a standard car or are there any special procedures needed for an XM?

Mine should be the same bendix system as yours in which case these may help.
The first shows the 4 pairs of contacts (two for each sensor) the pairs are stagered and paired up top to bottom.

CIMG2343 by Deanxm, on Flickr
Here is a high quality drawing to illistrate further

CIMG2342 by Deanxm, on Flickr

Should read about 1200ohms from memory and never write off a sensor, if its not the connectors causing the issue it is usualy the sensors own lead length.

good luck
D

That was useful thanks Dean.

Only thing is the second set of pins is for the OS rear (rear driver's side) not NS rear.

I tested the pins with a multimeter and pairs 1, 3 and 4 showed 2.73 on the multimeter (not sure how many ohms that is) but pin pair 2 had no effect.

Thinking this was the NS rear as per your diagram I removed the NS rear wheel & unplugged cleaned up the connectors. I tested the from the connector to the sensor & got a 2.73 reading again but when I tested the opposite connector I didn't get any reading so I assumed there was a break in the wire somewhere.

However I decided to check the OS rear anyway and when I tested the connector to the sensor there was no reading at all. Testing the pins back at the ECU still gave a reading of 2.73 at pin pairs 1 3 and 4 so obviously pin pair 2 is for the OS rear not NS rear.

I can't seem to find any breaks in the wire between the connector to the sensor, so is it possible its a failed sensor? Whats should I do next?

Next you need to try and get the sensor out of the hub , Citroen thought it was a good idea to locktight them in which is nice also being an alloy housing they can be a bit tight.
Rear sensors are fairly cheap but fronts are not, if wiggling the lead lenght doesnt give continuity then it will have to be a new sensor.

Strange on the pinouts, mine were that way round but it was a 92 car.

D

Mine was a S2 but I think that the 2.5s use a different system although I would think the pinout would be the same.

Peter

I thought it was a case of unpluging the sensor wire not removing the hub or have I got it wrong?

Can I fit a used one, as I may have found one from a matching car.

Secondhand ones need to be checked before you install.
Check the resistance before you buy.
Plug it in unfitted as a check to see if the start-up test completes and the ABS light goes out. Could save yourself some grief in finding it was iffy after you have bought and installed it.

John

Can you just replace the wire that goes from the hub to the connector or does the hub have to come off as well?

The sensor is mounted in the hub and you dont have to take it off to get to the sensor, you may however have to unbolt and remove the wheel bearing assembly to hammer the old sensor out from the inside, then you can run a drill bit through the hole or sand it back to clean it and grease before inserting the new one.

You can replace just the lead if that is where the problem is, if there is high resistance or no continuity but when you wiggle the lead length you get the correct resistance then that should be easier to sort out.

To be honest one of the rear sensor issues is trying to get to the connector on top of the subframe.

D

I had no trouble getting to the connectors on top of the subframe, just had to reach my hand through amid horrible fears of the car dropping down on me & the brake disc slicing through my head despite having the car supported by a trolley jack AND an axle stand. I get extremely nervous working underneath cars especially this one where I don't really understand why the suspension will sometimes lower itself when its jacked up!

I'm thinking of getting myself a pair of wheel ramps so I can have a good poke around without worrying about the car dropping on me! If I had the car up on the ramps, once on the ramps should I lower it to the low suspension setting or leave it on normal?

Nigel

The most useful thing I have ever built is this ramp (if the picture has posted) if you have some sloping ground it not difficult to construct. I have been using it for the best part of 40 years now and it makes working on the cars so easy, you are at exactly the right hieght for brakes and suspension and I sit on the little stool to work underneath. Its not as good as a proper four poster but almost.

Peter

Don't seem to be able to post the picture for some reason.

Wouldn't mind seeing a pic of that, I've got some sloping ground here. I'll pm you my email address & see if you can attach it as email?