Any ABS Gurus?

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c.morewood
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Any ABS Gurus?

Post by c.morewood » 09 Nov 2012, 17:28

I've had the intermittent ABS light for a couple of weeks but last night the light came on and stayed on.
Today I've been through a number of threads eliminating causes.. but the light is still on after a run this afternoon.
Here's what I've done:
I checked the resistance of all 4 sensors...this thread.
http://www.frenchcarforum.co.uk/forum/v ... hp?t=26012" onclick="window.open(this.href);return false;
Thanks Red-Dwarfers.. eliminating a sensor fault at the same time spraying the contacts with cleaner.
The results were 1040RL 1040FL 1060RR and 1100FR Ohms

I've been through the fault finding on this thread
http://www.frenchcarforum.co.uk/forum/v ... =3&t=38894" onclick="window.open(this.href);return false;
Thanks xmexclusive
Checked the F1 fuse in the engine compartment and the F6 inside the car.
However I can't find any reference to a relay.
The light is steady and does not blink when I switch the ignition suggesting that it is failing the static check.
I was wondering if there are any ABS Gurus out there who could suggest where to look next.

Thanks,
Chris

lurchy666
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Re: Any ABS Gurus?

Post by lurchy666 » 09 Nov 2012, 17:43

if you could find a member local to you wiv lexia, they could plug it in and tell you exactly whats wrong with it,

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Old-Guy
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Re: Any ABS Gurus?

Post by Old-Guy » 09 Nov 2012, 18:27

At the risk of asking an idiot question; have you checked that the state of the plug and socket at the ABS ECU? This is just behind the battery and if the seal on the plug isn't perfect, salty moisture gets in and corrodes the contacts - a common source of problems. Typically, if you use a Lexia the ECU fault code will indicate a faulty sensor which you replace at vast cost without solving the problem. Then someone suggests you check and cleans the contacts in the plug & socket - which, if you'd done that first, would have saved you the price of a new sensor.

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DickieG
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Re: Any ABS Gurus?

Post by DickieG » 09 Nov 2012, 18:39

You may have an intermittent fault which you really need a Lexia to accurately diagnose, generally the front sensors fail far more regular than the rear ones and looking at the readings you've posted one stands out (FR) so I wouldn't be surprised if that one is the cause of the ABS light illuminating.

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Re: Any ABS Gurus?

Post by c.morewood » 09 Nov 2012, 19:53

Thanks .
Old guy.. Red-Dwarfers thread covers the corrosion issue.. it looks pristine in there .. but just in case I sprayed contact cleaner.
DickieG .. I was wondering about that .. how much tolerance is there on the resistance? I read on one thread that it should be about 1080 Ohms so I have 2 under reading by 40 one under reading by 20 and the other over reading by 30.
Lexia isn't really an option at the moment as the nearest member with one is in Dundee about 70+ miles away.. I may have to invest in one myself. I just wondered if there was something easy that I may have overlooked.

Thanks again for the replies

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reblack68
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Re: Any ABS Gurus?

Post by reblack68 » 09 Nov 2012, 20:41

Have you checked the rings on the CV joints? My Xantia, exactly the same model as yours, had the same issue and it turned out that one of the rings had cracked. Eventually it shed the ring and the light was on permanently until I replaced the CV joint- at the time I couldn't find anybody selling the rings separately.

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Re: Any ABS Gurus?

Post by c.morewood » 09 Nov 2012, 20:45

Thanks Richard.. I'll check them in the morning

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Re: Any ABS Gurus?

Post by citroenxm » 09 Nov 2012, 22:04

If all your sensors are fine and fettle then there only one thing left on Xantias that DO PACK UP.... The ABS ECU itself! And they do, as I have changed 3 now over the last ten years.. Not many I know, but I have. Infact, one very recently on the Estate car Im dooing up

This is for Tevis on Mk.1 cars, which is different to S2 cars. However, thats not to think an S2 ECU has packed up.. Ive just not come across an S2 one packed up yet...

Thats what I would be changing next...... :wink:

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Re: Any ABS Gurus?

Post by Hell Razor5543 » 10 Nov 2012, 18:03

If the reluctor rings are cracked, you might want to consider these;

http://www.ebay.co.uk/itm/CITROEN-XANTI ... 27c0132920" onclick="window.open(this.href);return false;

Hope it helps

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CitroJim
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Re: Any ABS Gurus?

Post by CitroJim » 10 Nov 2012, 18:13

The front right sensor at 1100 ohms looks high to me Chris. My experience is there's little resistance tolerance on Teves systems.

Be happy it's one of the front ones. the rears are devils to do...

Early MK1 sinkers had ABS ECU issues but the later MK1 and MK2 ones are generally pretty reliable in my experience.

The ABS reluctor rings are much easier to fit than it first looks. Bake them at gas mark 7 for 30 minutes in a pre-heated oven (make sure SWMBO doesn't see you!) and they slip on a treat...

c.morewood
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Re: Any ABS Gurus?

Post by c.morewood » 10 Nov 2012, 20:51

Well it looks as thought it may be the ABS unit its self. We had a good look at the front reluctor rings and no cracks could be seen..cleaned them up just in case.. they weren't in too bad a condition .. had a feel of the rears and also couldn't feel any cracks. I tried an ecu reset..+ and neg battery leads together.. can't remember the correct name for it and the ABS light came straight on and stayed on with no check... took the car for a little run, over 30 mph, but that did no good either. So it looks like I'll have to get in touch with DickieG and get a lexia ordered.
Jim the problem doesn't seem to be the sensor as according to xmexclusive's thread there's no blinking to check servisability.
"

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Re: ABS warning light/sensors/ECU/wiring problems

Post15 Mar 2012 13:47
There are two seperate ABS checks carried out by the ECU.
The dynamic ABS check is the one that needs 4 good sensors and a moving vehicle above a set speed.
A resistor replacing a sensor will not fool this dynamic part of the ABS test.
This test happens at regular intervals as the car is driven provided no brake application is being made.
When it sees a failure it records a temporary fault in the ABS ECU.
Get enough temporary faults and the ECU locks the ABS out permanently.
Get just the occasional fault and the ECU will clear itself by driving above the cut-off speed for that type of ABS.
Use a LEXIA and you can clear that fault record but not the original fault, you still need to correct that.
The Lexia cleared ECU might just get you through an MOT though.
This part of the ABS ECU check needs to be fairly fault tolerant as it is counting individual teeth on the ABS rings and comparing the results.
For example fractional wheel spin on a pot hole or drain cover will put up a temporary fault that quickly clears so no ABS light comes on.
A split ABS ring on the other hand will most likely show a fault nearly every wheel rotation.
It will quickly build up enough temporary ABS faults to lock out the ABS and put on the ABS light.
To get to see these dynamic ABS indications the ABS has to pass the static ABS check first.
The ABS Blink sequence on ignition switch on indictes only that the ABS has passed the static test.
If the light does not blink on ignition switch-on the fault is not just a defective sensor.
For the static test of the sensors the ABS ECU only checks the resistance of the sensors.
A resistor instead of a sensor will fool the ECU at this stage.
But sensors are also the final stage of the static test.
If the ABS light has not already blinked a couple of times it is failing the ABS static test before it gets to the sensor check.
So no amount of work on sensors alone will cure this type of fault.

From memory the earlier stages of the static check are:
Power supplies;
ABS saftey relay correct operation;
Microprocessor running test;
Second Microprocessor data agreement:
On a typical ABS system the first blink of the light is the correct completion of the power supply check.
Note that some ABS ECU's have up to 3 seperate fused feeds.
If any one is down for fuse or poor contact there will be no ABS light blink at all.
It then checks the ABS relay.
Pass this test and you should get a second blink of the ABS light.
Now the ABS relay also controls the power feed for the ABS light so in one fault condition it too can cause no ABS blink at all.
The third ABS light blink confirms that the Micro checks have completed ok.
The ECU now checks the resistance values of the 4 sensors.
It then starts again and repeats all the checks from power to sensors.
If these pass ok the ABS light will then remain off.
If it fails the light will stay on.
In most of the UK reaching this stage should get you a MOT pass (NI is the exception).
So for the initial ABS fault finding:
Ignore the sensor and forget about the Lexia just watch the ABS light blink on ignition switch -on.
Count the blinks if any and from that work out which bit of the circuit to check.
The process requires no test kits just a few minutes logical checking.
If you need to move onto sensors you will be there in less that 5 minutes.
Sensors can take you hours to work through and correct.
Thats the stage for the Lexia or meter.
Do not waste time on the sensors until you are certain they are at fault.

John
"

Does anyone know where the ABS relay is located?
Thanks for all you inputs.
Chris

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DickieG
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Re: Any ABS Gurus?

Post by DickieG » 10 Nov 2012, 21:50

The ABS relay is the dark green one located in the engine bay fusebox behind the battery, I'd still bet on the fault being down to a duff sensor (O/S/F looking at your resistance readings), I've changed many of them where they pass the resistance test but fail in operation and just like Jim I'm yet to hear of a S2 ECU failing, AFAIK ABS ECU failures were mainly on early cars as in pre 95.

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Re: Any ABS Gurus?

Post by citroenxm » 10 Nov 2012, 21:59

Mainly S1 Tevis Up to 1997 P reg, as the recent ECU change I swapped was on the P reg Estate... So the Long Black ECU ones fail.. I agree S2 Tevis 20 ECUs seem to be good ones, Im yet to see a failed one..

c.morewood
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Re: Any ABS Gurus?

Post by c.morewood » 11 Nov 2012, 10:01

Well would you believe it?
I went to pick the wife up from work last night.. the light was on all of the 15 miles there.... but I had to wait about 10 minutes for her to come out of work with the engine off but ignition on.....when I restarted the engine the light went straight out... with no blinks as a check.. it has remained out his morning... Fingers crossed!!!!

Should it return I think I'll replace the sensor as DickieG suggests as they're only about £15

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Re: Any ABS Gurus?

Post by c.morewood » 12 Nov 2012, 10:14

I thought it was too good to be true... it was back, bright as day at 5am this morning.. EBay here we come....