ABS light 'No function' but no ECU fault code, how clear? BSI?

[captainkephart]

Hi FCF Team,

I have looked to see if this question is covered elsewhere, but don't think so? Sorry if being dorf!

On a 2009 Xsara Picasso petrol 1.6 DOHC.

Turn on ignition and even before engine start the car beeps once and the 'ABS fault non-function' message comes up.
But car drives normally and the light stays on all the time.

OBD reader says there's no faults (temporary or otherwise). However, I 'cleared', just in case it's some hidden thing.
No change. Is a BSI reset needed?

Looked at reluctor rings and the ABS sensors, can't see anything wrong. However, the front nearside reluctor has triggered this fault in the past (rusty high spots which I filed off the rings). Could they have damaged the sensor? How would I know? Maybe it's as simple as that ... in which case apologies for taking up your time.

Any suggestions? Thanks, Capn K

[RichardW]

I think you'll need a better scanner....

Whereabouts in the Borders?

[captainkephart]

Hi Richard,
West of Tewkesbury ...

Scanner I've got is the TOAD one, which enables you to select Citroen / Peugot fault codes.
Worked fine on the 2008 version of the same car (the Desire 16v) ... it showed up all the oxygen sensor faults!
Is 2009 version different? The live data works just fine on it ...

Thanks ...

[RichardW]

Ah, wrong borders....! I was going to offer Diagbox, but I am some way away from there. Can you see live data for the ABS sensors?

[PaulC5]

To read ABS fault codes needs a scanner that obviously does them and would be listed in the sales info. Most cheaper ones only read codes that affect the engine emissions.

[captainkephart]

Richard,
Thanks for the offer.

Re live data, it shows the vehicles speed correctly. I assume that means it's reading the sensors OK, or not?

[GiveMeABreak]

If the wheel speed sensors are working OK, you should see the speeds as similar on the live data and you would get a fault code for a faulty wheel speed sensor on most scanners if it can read the ABS ECU.

Cruise control (if you have it) would be deactivated if there was an issue with any of the sensors too. So may be something else that is triggering the warning - but it really does need interrogation with Lexia / Diagbox.

[captainkephart]

Thanks very much Marc,
I'm talking to my local super-expert car engineer this afternoon, to see what his equipment says (and he knows this car).

[captainkephart]

Hi,
I've had the car (Xsara Picasso 2009 1.6 DOHC petrol) checked with a professional OBD tester, which says no faults / no temporary faults. Cleared anyway.

I've replaced one ABS sensor (n/s front) which had been damaged by something.
Reluctor ring fine, no cracks or missed segments.

When I turn on the ignition, ECU does self-check, lights go out; start engine and after about 5 seconds one beep and then the 'ABS fault - non-function' message comes up - and stays on, even when driven some distance (50 miles, parking engine off) and on again several times.

How do I get ABS fault light to clear? OBD still says No Fault!

Thanks for any help. Capn K

[GiveMeABreak]

You have to be aware that not all generic code readers work properly with all vehicle systems. You really need Lexia / Diagbox for a diagnostic as these can read all the fault codes and provide live data. Many after-market units can't read some of the ECUs like the ABS system, which doesn't mean there isn't a fault code. The ABS system should log all faults and there will be a history that you can read using Lexia, that shows the code and how often a fault was triggered, which is useful for temporary faults.

It's very possible you have a faulty wheel speed sensor, but knowing which one is obviously essential. If you can get it diagnosed with Lexia / Diagbox this will likely tell you what the fault is.

[captainkephart]

Thanks Marc,
It was read with a top quality professional OBD sensor, I assume like the Lexia, as you suggest.
And a faulty sensor (physically damaged) has been replaced.

Will the ABS light go out if I disconnect the battery for more than half an hour?
Thanks.

[GiveMeABreak]

Hi, no unfortunately not. The system has a self-test function which it goes through every time the ignition is switched on. At any time there is a fault with this system, it will flag up the warning and can also disable some of the ABS features until the vehicle is stopped and the ignition switched off.

[captainkephart]

Hi Marc,
Thanks. Well, I'm stuck then.
I've a friend on the industrial estate who tunes and races cars, maybe his reader will find out what I've missed so far?
Ciao, Capn K

[GiveMeABreak]

It's one of the more common faults we see of some non Lexia / Diagbox diagnostics not being able to read ABS / ESP ECUs. I don't know what your friends diagnostic capabilities are, but they may not be able to read the historic memory log of stored faults either - just depends. So if it is a temporary fault, again, it may not be active when you have switched the vehicle ignition off. So my advice is to drive around for a little while and get the fault active, then leave the engine running whilst scanning with the diagnostic to see if it will pick it up then.

[captainkephart]

Hi Marc,
Thanks again. I'll do that ...
and report back later in the week.