I developed a simple test method to check the wheel sensor output on the car. You do not want to go around swapping bearings and hubs unless you are sure!
I will post a full write up when I have replaced the bearing for the second time. At this stage I would say know where the sensor ring is on the new bearing. It is a thin plastic polymer ring impregnated with ferromagnetic material, AND VERY FRAGILE. Mine was coloured brown. You can make absolutely sure with a small compass. The trade use a clear plastic envelope with iron filings.
When you buy a new bearing, look over the surface of the ring very carefully with an eyeglass magnifier and reject any bearing that has pit or score marks in the surface. Also, make sure that whoever presses the new bearings into the hub and carrier, does not use press tools that could damage the surface of the magnetic ring or place it on a press bed that is dirty with metal filings or swarf. Re-check the sensor ring with a magnifying glass after assembly on the hub. Next time I shall stick Sellotape over it before it goes to the press shop, which will make identifying surface damage a lot easier.
I did not find much info about actually removing the hub and carrier and there are plenty of opportunities to damage the magnetic ring and empty gear
all over your driveway!
On my Laguna 1, the drive shaft drops and is still under tension from the suspension spring with the road wheel appearing to be fully down. Attempting to pull off the hub ends up in a bit of a 'boing' and crash. I now put on the spring compressors with the wheel loaded so the hub can stay fairly horizontal to the driveshaft when it is pulled off. Nothing said about that in Haynes! I can see plenty of opportunities to damage the surface of the magnetic ring as you are fiddling about trying to get a hub with new bearings back on the end of the driveshaft. Haynes warns about removing the wheel sensor but to be honest, the most important and fragile part is the magnetic ring on the rear of the bearing.
This SERV+ABS fault linked to wheel sensors is a nasty one to confirm if it really is the bearing magnet ring and you need to handle that side of the bearing VERY CAREFULLY. There are 44 (maybe 42) impregnated 'magnets' in the ring and if only one is damaged, the ABS computer will throw up this fault because it is checking the time of each pulse. My car is a Laguna 1 but I suspect they use the same principles on the Laguna 2.
As far as buying a used hub from the scrappy is concerned, if they have not taken care removing it and tossed it in the bin with other parts, the magnet ring could have been damaged. If the ABS wheel sensor fault does not clear, then do not go looking for other things.
Watch this space for a follow up.