Fed up in St George

We had our rack and pinion go out, thankfully no one was injured, 2014 gmc sierra 1500. We replaced the wiring harness to the rack, the battery, the alternator, and now we are looking at the control module. It is is hit and miss with the steering. Go out and start the truck, no power steering, 15 minutes later try it again and you have power steering. We have checked all the connections, had it calibrated at least 6 times, and still trying to track down the problem. Any thoughts?