I was recently getting 13.1 errors... thought the paper path was clear... on disassembly, I found one little piece of paper wedged BEHIND the paper sensor, keeping it from moving.
Chances are you've got a similar issue. The other thing I've seen happen is that since they use optical sensors, a build-up of paper dust in the sensor will cause it to think there's a jam. Try blowing out the optical sensors with some compressed air.
Just my 2¢
"In order to start solving a problem, one must first identify its owner." --Me
--Greg