I have installed a Holley Terminator X Max on a e38 ecu/t42 tcu Silverado. The Silverado starts up fine with the key and stock key on ignition system when the main factory transmission plug is plugged in, but will not start without it being plugged in and the Terminator X Max Transmission harness plugged in. I have cleared, what I thought, were the checks with HP Tuners but still no engine turn over with the key and Holley Terminator X Max Transmission harness plugged in. The things I removed were starter fault checks in the os tab, starter diag in system general, no error report p1631, both vats disable and write entire. Still wont start without the oem harness plugged in. I am looking for any help to get the factory key to turn on the truck with out the factory Transmission harness plugged in. I presume there is a wire in the main transmission harness that needs to be powered or grounded to pass an ecu check, or I didn't clear everything in HP Tuners to get this to work. Thank you for any help.