crank. position sensor question.

my truck developed a random misfire over the past 6 months, really bad @ times and could not connect any set of circumstances to the misfire. I thought I would check the CPS ,so I took it offand found what looked to be a rubbing mark on the surface of the CPS. What could cause this?? A warped trigger wheel? If moisture builds up on the wheel would it cause a misfirecondition??
thanks in advance,
Ron

A warped ring is a possibility. Dirt, sand, gravel, etc. could also cause the rubing. There is very little clearance between the ring and sensor.

I would not expect moisture to cause an eroneous sensor reading, as it is magnetic, and water shouldn't affect a magnetic field. If the water were to freeze on the ring, this could also be a source of the marks.

I'd start with posting year and engine!

So sorry thought I did that . Its a 1997 C1500 2WD Vortec 5.0,with a 137,000 miles.
Thanks.