Xantia series 2 ABS problem.

MJM · Post by **MJM** » 21 Aug 2009, 09:41

Can I have a few pointers, please? It’s a series 2 1999 Xantia 2 litre petrol.

The ABS light has just come on. For a few trips it has behaved haphazardly, sometimes on then going off or coming on and staying on.
My first thoughts are to check the wheel sensors. I am assuming that it should be possible to read some value of resistance to check for either open circuit or short circuit from each sensor.
I think the abs ecu is located either in the centre consol or behind the glove box. Can someone confirm this, please? I also want to check the connectors situated near the wheels. Whereabouts are they? From some of the trailing arm posts I am assuming that the rear ones are somewhere under the back seat. The fronts I am also assuming are in the wheel arches or engine bay.
What sort of resistance value am I expecting to see?

The fact that the light does not go out suggests that the rotors are ok. I am hoping, given the fact that the system sort of failed over a couple of days that it is either a broken sensor wire or a bad connection.

I have owned the car for 6 years and this is the first running fault to appear so I don’t mind applying a bit of tlc. It’s just nicely run in at 104k!

Post by **CitroJim** » 21 Aug 2009, 09:57

Hi MJM,

Yes, the best and first thing to do is to measure the resistance of the sensors. They should around 1039 ohms and this needs to be quite precise. Less or likely more means they are faulty. I've had them not work but still reading around 1,120 ohms.

The ABS ECU is located between the engine bay fuse box and LHM reservoir. It's attached to the side of the ABS hydraulic block.

Easiest way to check the sensors is to measure them at the ABS ECU plug after removing it from teh ECU (ignition off before removing it).

Then using a good digital meter, measure each sensor at the ECU plug as follows:

LH front: Pins 1 and 2
LH rear: Pins 5 and 6
RH rear: Pins 22 and 23
RH front: Pins 19 and 20

The pin numbers will be seen if you look carefully at the plug base.

Each sensor is connected into the main loom vai a two pin plug about a metre away from the sensor itself. It is worth checking these connectors before writing off a sensor completely.

MJM · Post by **MJM** » 21 Aug 2009, 11:55

Thanks, Jim. I've armed myself with a digital meter (I've got one of the heavy old AVO anologue meters in its black box at home). If I can make some reasonable progress on the bathroom renovations and the weather gods decide to shine then hopefully an hour or so should pinpoint the fault.

Malcolm

Post by **CitroJim** » 21 Aug 2009, 12:06

Good stuff Malcolm

Normally I use my trusty old AVO for nearly all electrical jobs but sadly, good as they are, they're just not accurate enough for ABS sensors

MJM · Post by **MJM** » 21 Aug 2009, 19:35

Well, the abs light was on for the morning commute and 95% of the return journey. I stopped at the local shop for a packet of smokes, restarted the car and the light went out. I drove home, stopped the engine and restarted it. Normal light behavior. My wife used the car to go shopping this afternoon and it was normal behavior again.
It's beginning to look like a dodgy connection. Perhaps the dry weather upset it and the heavy storm I drove through on the way home has rejuvinated the connection??

I hate intermittant faults.[/img]

MJM · Post by **MJM** » 23 Aug 2009, 12:18

Well I've probed the sensors, three are reading ok, close to Jim's spec. One is reading open circuit, the left hand front. I would appreciate some guidance on locating the sensor connection into the main loom. I've removed the airbox for a better view but still can't find it. A photo or diagram would be greatly appreciated.

Slightly off topic, how does one insert emoticons into posts?

Malcolm.

Post by **myglaren** » 23 Aug 2009, 12:52

MJM wrote:Well I've probed the sensors, three are reading ok, close to Jim's spec. One is reading open circuit, the left hand front. I would appreciate some guidance on locating the sensor connection into the main loom. I've removed the airbox for a better view but still can't find it. A photo or diagram would be greatly appreciated.

Slightly off topic, how does one insert emoticons into posts?

Malcolm.

When you are composing a post they are grouped on the left just outside the reply box. Click to insert or if you know the code just type it straight in, i.e. : roll : (without the spaces) gives you

and : ) =

Someone else will help you with the sensor leads, I haven't a clue

DickieG · Post by **DickieG** » 23 Aug 2009, 13:16

Remove the N/S/F wheel and having located the sensor follow it's lead alongside the front subframe where tucked alongside the brake pipes you will find the connection plug/socket. On some S2 Xantia's (V6 for example) the plug is tucked right behind the subframe on it's blind side.

BTW the N/S/F sensor is the most common one to fail.

VertVega · Post by **VertVega** » 23 Aug 2009, 13:44

This picture was taken in another occasion but abs sensor connector can also be seen (I hope) amongst all the dirt

This is the front left side.
Some more clues: gearbox drain plug, inner cv joint and at the background part of steering rack gaiter.

Before replacing sensor, measure resistance value also from this connector to confirm that sensor is broken.

MJM · Post by **MJM** » 23 Aug 2009, 18:12

VertVega, excellent photo. I've got it spotted.

The brake pipe hanging below yours is clipped just below the sensor on mine. I've run out of time this weekend (shmbo says that bathroom is more important for some reason) I want to swap some wheels around to even out some tyre wear so it will be two birds with one stone with a bit of luck.

myglaren, thanks for the tip. I don't know if the emoticons show up when I'm writing the post but I've tried a very happy and it shows as a space then

in the first line.
Being a bit of a computer nerd I may have something turned off or on than shouldn't be.

I'll update when something happens.

Thanks for the help so far!

MJM · Post by **MJM** » 23 Aug 2009, 18:15

Yes! the emoticons worked

. It should be swmbo not shmbo. (Finger trouble

Post by **myglaren** » 23 Aug 2009, 18:26

MJM wrote:Yes! the emoticons worked . It should be swmbo not shmbo. (Finger trouble

They should appear in preview.
You should also be able to edit your post if you see any mistakes after submission but IIRC it is time limited.

VertVega · Post by **VertVega** » 23 Aug 2009, 19:15

Thanks MJM, I'll clip mine as well. I didn't notice it before. Things are quite camouflaged down there

MJM · Post by **MJM** » 06 Sep 2009, 17:38

Well, I've disconnected the sensor and it's gone open circuit. From the way it failed I'm guessing that a wire has broken inside the lead after 104k miles of flexing.

I checked the loom back to the ecu from the connector and that's ok.

It also proved that the meter was working.

How much should I be paying for a new one, and where from?
I'd rather buy new than used.

Thanks for the help so far.

Whilst I was under there I noticed that one of the hydraulic pipes running across the car was showing some surface rust so that got a good clean and a coat of grease as well.

VertVega · Post by **VertVega** » 06 Sep 2009, 19:12

Some years ago I paid around 70 EUR (61.0944 GBP United Kingdom Pounds from currency converter

).

Edit: You can buy ABS sensor from a scrapcar. Remember to test it on site. Another option would be ebay. Sometimes there are also very good price offers.