2005 suburban 1500 electrical issues.

Hello I have a 2005 suburban 4x4 with what I think is an electrical short somewhere. The truck runs and drives normal. But the check engine light and security light go on and off randomly and we get error when trying to use an obd2 tool. One symptom I notice is that when you hit the door locks only the rear doors lock not the front and when you hit unlock the locks make the unlocking noise 5times. My abs,brake and traction control light are also on but they just stay on never go off. The bcm and ebcm replaced already at dealership. Any help would be much appreciated.

Update*
I located the splice pack under dash removed the pins until I got communication with obd2. The pin was pin C which has 2 wires going to it a blue and a green/white stripe wire. In the Haynes manual I bought it says those wires go to the ebcm and the bcm. Was thinking of cutting them and reconnecting to see which one is the problem is that a good idea? Or how do test each component?