I am a first itme diesel owner as of July. My truck is a 2013 3500 duramax with 57,000 miles on it. Recently it pulled a NOx code. Teh diesel shop I am taking it too said new sensorts are $370 a piec...
Start here and google to tell you how to clean the EGR system on your truck. Once you get things apart pour some Purple Power (cleaner/degreaser sold at autozone for around $8 a gallon) in and let it soak. Rinse with hot water and blow out with an air hose. Once the system is clean you may find the sensors are doing what they should be doing. Telling you to clean the system.