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'Our' 2.2 HDi GTX has an intermittent ABS fault which can pop up every few seconds, or stay on for ages depending on the mood it's in. It somehow sneaked through the last MOT like this, but seems unlikely to fair as well next time, (October).

I've had PP2k hooked up to it and it shows no faults, even when it's generating the alarm as you watch. Tried clearing the faults, makes no difference.
When you interrogate the ECU characteristics, (or whatever the term is), it reports a product code / serial no. so I assume this confirms PP2K can 'see' it.

The fault usually appears after the self-test and can pop up with the car stationary, so I think that rules out reluctor rings.

I'm wondering if it might be intermittent comms between the ABS controller and BSI or engine ECU, (whichever it talks to), maybe this message gets triggered if the ABS doesn't communicate?

My bro is buying this car from my daughter's partner and for a little while still has access to his old 2.2 exec that expired in France last year, so could get some bits from that if we can identify what might be useful.

Any ideas or suggestions welcomed/

If PP2000 cannot give you a definite 'corner' where the problem lies, try the footwell connector...
The signal from the rear abs to the abs block can be disrupted here.
As you said, I believe a dodgy reluctor ring will pop a fault when moving, not at the self test - so I think it's a wire issue.
This was the issue with Sonia's car, took 2 years of trial and error but the fault was a tiny bit of corrosion in the connector - the car was dry underneath the carpet so it wasn't obvious.

Thanks Kelv, I'll check that out.

A couple of other observations - it doesn't have ESP, cruise & stoplights work, so I guess the pedal switches are in the clear.