First...hello and thank you for having me to the site. Been surfing the internet for couple of days trying to get some ideas what could be wrong with my car and found this site, hopefully someone has some idea for me. '04 Cadillac CTS 3.6. started to completely stall out of the blue no warning no warning lights, just die driving or at idle restart fine. Couple days later problem advanced to loosing all dash lights, speedo, tach and turn signals when car would restart. Now when i turn car off and remove key car is still running, sometimes for a few seconds, sometimes i have to disconnect wire harness from fuse box under hood to get it to shut off. still no dash indicators, speedo, odometer, tach ect and low power on acceleration, cooling fans stopped coming on and car over heat, AC cuts off and just blows hot air intermitantly. Does this sound like ignition switch? if so the electrical switch or key assembly? Thanks for any input. (btw took to autozone to plug into computer...no codes received)

wondering if all the systems i mentioned malfunctioning all run through the ignition switch...if so I can almost be sure this is the problem...esspecially with the car still running with key out?

Hm i personally have never encounterd something like this..makes me wonder if it is part of the ignition switch or even the computer?I will see what i can come up with for ya

looks like pin 5,4, and 3 should be hot with the key in run and go out when you turn the key off.

Reading that my first thought is a bad ignition switch. I say test it with the above diagram.

This diagram is just what I needed...thank you so much. I'll start tracing it down and reply back what I find.

replaced ignition switch this afternoon. Still the same problem. I'm at a dead end now...next stop dealership.

if you didnt already take it, take a look at that ign 3 relay maybe swap it with another, if you have let us know how you make out

already dropped it off at local mechanic for a quick check before sending to dealer. I did mention the IGN relay'* for them to check as well. After pouring through pages of wire diagrams though I'm beginning to think it could be a PCM problem...I let everyone know what they find.

incredible update...car shop called and told me to come get car..they had ran all diagnostics and there was nothing they could do...all major systems had shut down computers dead, modules not responding and I was looking at thousands of dollars of repairs above their capabilities...I was in despair and about to cry...started shopping for a new cts.

Last couple of days I have been pouring over wire diagrams on the entire car and trying to find a common denominator besides the ignition switch i already replaced. Three things constantly came up.
1. ECU
2. Interface plug in
3. Ignition 1 relay

Car shop mentioned that the underhood fuse board was half dead problem needed to be traced down to exactly what module shorted everything out...it made sense but didnt.

I kept thinking about what jwfirebird said about ign 3 relay and had nothing to loose so when i got home i started to swap relays...here comes the incredible part....swaped out ign 1 relay with high beams relay(one i know worked and could do without temporary)....and voila!!!!! everything came back up and works like new.

thank you everyone for the ideas and determination not to sit on my butt and scratch my head...only bad part is I did see a nice cts-v I coulda been in if i wanted to stop paying my internet bill