P0708 GMC -

Question

This code keeps coming back, even after the replacement of the internal range selector and harness. 2009 GMC 2500 HD Duramax Allison

Answer 1

what do you mean by internal range selector? the NSBU (neutral start back up switch) see picture below 

usually other people that have a similar replace the NSBU (neutral start back up switch) but they dont have all those other codes.

if that is the part you have replaced already, I would replace the transmission fluid and filter.