Abs faults

[Athorpe]

After a little advise here,

I've been getting a right rear AbS fault showing, first I replaced the wheel bearing as it was showing out of range not a circuit fault. Although the bearing/hub had only done 800 miles prior to the fault

That briefly cleared that fault code and now I get circuit fault, so replaced the sensor, which cleared the fault for about 3/4 mile and now circuit fault is back.
While it was clear and pressure on the brakes lead to the dab kicking in, for no reason at all

On starting the car now the abs fault warning comes up, but within a few feet it goes off, only to come back sometime within a mile or so, how long it takes seems random and the code is circuit fault right rear.

Anyone any ideas where to look, I can't see how it's intermittently got a circuit or not. I'm thinking sensor issue still since it's kicking the abs in even on light braking until it fails again ?

[Mike Noc]

Check for any rust where the sensor bolts into the rear hub - it can lift the sensor away from the magnetic reluctor ring in the bearing, and the air gap is critical.

On one aftermarket rear sensor I had to file the bracket down which had the effect of moving the sensor head 1.3mm nearer to the reluctor.

[Athorpe]

Thanks that's was the issue, mounting boss on sensor to thick keeping it away, filed down and now it works.
Why that caused an intermittent fault, or a open circuit fault code doesn't make sense to me, but it's done 70 miles and still workin