Not sure what you need on the Mac Hall Sensor. I have quite a few 250's that are about 10 years old. Never had an issue with the sensor. Even when caked with dust and fog juice, they still worked. Only when they aren't lined up do they not detect the magnet on the wheel. Every time I think a sensor is bad, it always ends up being the wiring in the tilt yoke.
I have seen the cold solder get weak on these sensors. If you are getting both errors, check the continuity on the sensor wire set to the head. it may have a faulty cable. You will need to order that wire set.