truck still in tranny shop. shifts 1,2,3 fine then starts to go in to 4th gear and light on overdrive blinks. everything in trans has been replaced. shop owner tells me when he tries to communicate with pcm it says error and that my pcm is bad. my sct does not show any codes. does the sct need to be installed . my custom tunes are the only ones that my truck will read because my strategy is still jan of 03. sct was in stock setting when it went to the shop.