SES light came on today so I took it to Autozone so they could
run a scan. It came back as a Camshaft position sensor. It must be a
dealer only item because they said that they dont stock it. My
question is, where is this sensor located and how much trouble is it to
change out? I can order one from GM Parts Direct for 39.00. Im sure the
dealership wants a good bit more for this part. Oh yeah, the truck is a
2001 2500HD crew cab with the 8.1 vortec.

Its on the timing chain cover under the water pump I not sure on how had it is to change I had the pump off doing a cam swap.

Cougar - That's a good price for that cam sensor --- I just checked here at napa, and the price is about 60.00....

I had to replace mine at 50k. The ses light came on and then a couple of days later I noticed the truck would start and then die after a couple of seconds about every other time i drove it. The sensor fixed it. The sensor was pretty easy to get at, remove the front skid plate and look on the timing chain cover. Theres one screw holding it in and a weatherpak connector on it. The sensor fits into a hole and has an o-ring on it. Mine was a real beech getting it out - had to pry on it with a screwdriver while I twisted it. Took about 30 minutes start to finish.

Thanks guys, I will be tackling this project next week.