I have am 06 envoy denali and yesterday when I started it up it wouldn't shift out of first gear without me revving it all the way up then it was followed by a very hard shift into second. I tried to put it in third or second gear and the shift selector indicator never moved. It just stayed on D. I got to my friends car lot , turned it off then back on and it shifted fine throughout the whole day. I used my torque app to read the codes. Says something about network. Is this a harness issue?