Crankshaft sensor positioner

My car's tachometer started dropping to zero, and eventually stop the engine. The car runs totally normal for several miles if driving. Then the tachometer starts bouncing off and on again.

My engine light does come on eventually, and my code reader says it is a crankshaft positioner sensor.

All of my research tends to say that a crankshaft positioner sensor is either bad or good.

Like I said, my car runs like a top until this tachometer bouncing starts, accelerates fine. It has stalled while idling in my driveway several times though.

The check engine light goes off by itself sometimes. I reset it myself many times though.

Thanks.