Hi. Hope you can help me. !I am willing to compensate properly if I can get the help I need. Here is the story..... I purchased a 2005 CTS
without the ECM also without the TCM. Then I PURCHASED BOTH ITEMS ALREADY PROGRAMMED. I think "plug & play" is the terminology. I turned the key and here is a list of what works and what doesn't:
DOES WORK: power seats, electrochromic rear view mirror, climate control heat and a/c lights up and you can adjust the controls and see it change on the screen ( but the blower motor does not work), headlights, taillights, brake lights
DOES NOT WORK: dash lights, starter does not engage, ignition shows no signs of working, power door locks do not work, power mirrors don't work, radio doesn't work
.I did replace the ignition switch and have no change in anything. I can follow your direction. I'm probably a 6 on a 10 scale for mechanic work. I do have a multimeter and know a little about how to use it.