Everytime I try to write in the vehicle OBD2 port it fails after bootloader. Scnner mode works fine and Reading ECM works fine everytime. I made a harness to flash with because the first fail left me unable to start my vehicle. If I unscrew the blue plug and plug in my homemade one in the vehicie it writes fine even without unplugging the green one. Still this is a pain in the ass. I do not have the stock radio but turn the aftermarket off. I turn off AC etc. It isnt voltage as I have 2 batteries and after using a power supply to flash the first time it failed I figured out I didnt have to remove the ecm from the truck and could just tap onto the stock battery for power with my harness. Please someone explain this to me, as it makes me very worried to flash it. Basically my Homemade harness has Blue connector, a power switch to orange wires, groudn to black/white and the purple wire from junkyard obd2 runs to green on pcm blue plug(pin 58). what could be interupting the signal on such a simple 4 wire setup? Can I splice a switch in for toggling between 2 obd2 ports and put one under the hood connected to only these 4 wires just for flashing?