Hello everyone, this is my first post here as I am stuck on where to go next for troubleshooting my issue. I have an 03' 6.0L 3500 express, it starts and dies immediately. Typically with a security fault code the security light should come on or blink. Mine never comes on although in doing a bulb test with a tech 2 clone, it lights up. Codes it has are P1626 (theft deterent start enable signal no recieved) and B2615 (passenger compartment dimming 2 circuit. I dont believe this has anything to do with it not starting). Worth noting also no lights light up in the instrument panel when the key is in the on position except for the battery light. Fuel and battery guages dont rise (it has about half a tank and battery is fully charged). Athough everything works when conducting a sweep test on the tech 2 clone. Parts changed with no effect- passlock senser (did both long and short relearn with GM subscription service), key cylinder with new keys, ignition switch, BCM (with program). Tested wiring resistance from passlock sensor to BCM, powers and grounds for the bcm, and the two data wires from bcm to ecm. I dont think there are anymore security related components to check or replace. I realize there may be an umbrella issue since other lights arent coming on when key is on (I'm pretty sure you should get a whole christmas tree light up when you turn key to on but dont have another chevy of same period to know for sure). Im hoping someone might have some insight on this because I can't find anything else to try. Thanks, Nick

Here is a video of what happens when I try to start it
https://drive.google.com/file/d/1pgi...w?usp=drivesdk