I just pulled the diagnostic codes on my van. It gave me a 4 or 44. that means? on 1995 GMC Vandura 2500

My van started to chug Friday night after a fairly lengthy trip. This morning, I pulled the codes to find out what the problem was. It gave me either a 4 or a 44. I'm unfamiliar with that code.

Asked by for the 1995 GMC Vandura 2500