Technical Stubborn Marea ABS light

[Brim987]

My 1999 Fiat Marea has an ABS fault that I can't get rid of.

Four garages couldn't even get the code, but I managed it with an old laptop.
Front Left speed sensor - changed that but no joy.

My local garage gave up because he couldn't get live data and recommends I scrap it.

An online Fiat parts specialist said it would be the reluctor ring, so I ordered that but it transpires
it doesn't have one - it's part of the wheel bearing.

My mechanic cleaned it up and said there isn't much to go wrong with them so there's not much point replacing it.
(???)

He did comment that the sensor only seemed to cover about half of the ring but it would have been even more labour
costs to check the other side for comparison - and, hopefully, it was like that with the original sensor (I don't know that ...)

After starting, the ABS pump comes on for the few seconds before the warning lights come on (and that turns the ABS off).

I'm desperate to save this car, it's my son's only link to his grandad, and has huge sentimental value.

Any thoughts appreciated.
Steve