First post, and thank you all in advance for any information you all may have. I have a 2015 Ram 2500, 6.4 Hemi. Starting last weekend I began getting the "Service 4wd" message on the information screen. Typically it lasts only a minute or two directly upon start up, then goes out. Today it came on and stayed on most of the day. I took the truck in yesterday to the dealer. They seemed stumped, checked all connections and said all was good. No codes when scanning the computer. Today it came on and off three times. I call them back, again met with a stumped sounding service manager. He said he'd discuss with his tech and get back to me. He called me back and said they were going to replace the powertrain control module. I'd like to be confident in what they are doing, but have to say, I sensed a lot of doubt in his voice with this suggestion. So, my question for you all is, does this sound right and have any of you encountered a similar problem?