abs please help!!!!

Hello again. My beloved p38 dse is going to be part exd (newer one). But last week I had a abs fault pop up which showed it to be a front passenger sensor. So I bought a new one. Changed it. But still the fault Is there. Do I need to reset it again. But I'm thinking it's a alternator fault as in the past week the diagnostic has shown up 'alternator fault' briefly, but only once on start up. Only once though? not since?
So, I'm asking. Do I need to get it rest to knock light off? Or could it be faulty alternator? Is there any way of knocking light off just to p/x it otherwise? Link it out etc. I'd rather fix it though. Thank you all, the joys of RR ownership never ceases to amaze me. So im buying another one. the fool i am.

Make sure sensor is seated properley, pads not excessively worn, check battery having stood overnight, volts output with engine running on alternator.........basic checks otherwise search threads