Hello and welcome to Just Answer. My name is XXXXX XXXXX X will assist you with your question.
If using a code reader, it most likely is not compatible with your truck. A lot of them do not seem to work properly with the diesel trucks, some will not pull all codes, some will not communicate at all. I wish I had a explanation for why this is, unfortunately, I do not. I even have one of the Mac Tools code readers that came out a few years ago and it is worthless on diesel trucks.
FIrst you will need a good scan tool to pull codes from the truck. Most likely you are going to have to perform what is called a "injector electrical test" or called a "buzz test" to pull codes for the fuel injection system. These engines are prone to have the connectors that are from the valve cover gasket to the injectors and glow plugs to come loose under the valve covers will loose there connection and can cause exactly what you are describing. There are other things that could be the cause of the concern, a bad injector or a issue with the Injector Driver Module, but this is the most common cause for what you are talking about.
If you need any other information just respond here and I will get back to you.