ABS Light on a 1999 2.5L
 

Hi all. Just got a 1999 2.5L and am very pleased with it. It's in excellent shape but high miles at 120K. I drove a Camry for 315K, still running but to many rattles and groans. I hope I can get similar service out of this Mazda. Anyway, my ABS light is on solid but no problems with driving the car. I looked through this forum and mazdaworld.org and found no technical advice so I'll ask here as there seems to be more technically inclined people over here. I had the oil changed and the shop scanned it and said a sensor was out but the scan would not indicatewhich one. This was just an oil change shop not a repair shop.

1. It seems to me a scan would indicate which sensor was out?
2. Is there a sensor on each wheel of this car?
3. Is it a magnetic sensor i.e. gear teeth and a pcikup?
4. Are they accessible to the average Joe?
5. What are the most common failure points in ABS for this car? chafed wires, lose connectors, failed sensors?
And lastly what would you do to diagnose and repair the problem?

Thanks.