I just came back from a 2000 mile trip. I noticed intermittently the little circle or O around the D on the shift instrument cluster was sometimes coming on and going off. I did not sense any change in the transmission shifting. I thought it might have something to do with the overdrive. I did not notice any changes except the light coming on and off,then it stopped. I was thriving with the cruise on 70'mph and I heard a clicking. The light came on and off. Anybody know what this is all about? Weird ! What is it trying to tell me?
John

 

Vehicle?

 

2006 3500megacab 5.9 diesel

 

If you didn't notice anything abnormal in trans shifting, or function. May have a loose connection on the circuit board on the back of the cluster.