2004 Cadillac CTS 3.6L Won't start.

Will not start how ? Turning the key to start ,what happens ? Does the starter engage an spin the engine but won't start an run or nothing happens .

I had something similar happen on my 2004 CTS. The car would not crank, and I recall the security light was on the dash. The key could be turned off, but not quite far enough to be removed.
The key can be removed by sticking a small pin or screw driver in a hole under the steering column... maybe 2 inches from the actual steering wheel. I recall there is a small cover or plug in the hole that needs to be removed.
You can let it sit and occasionally try to start it. My did start once more.
I ended up having it towed to the GM dealer and they replaced the ECM for about $500? That took care of it for a couple years, until I recently sold it.

There is none.Idle is controlled by your computer. If you have problems, check these. Vacuum lines behind throttle body. You may have to replace your air flow sensor. You can also try this:
Engine cold.
Turn your key to on position for a full minute. Don't start the car.
Turn key off for 10 seconds
Turn key on for 10 seconds. (Don't start)
Turn key off for 10 seconds. Then start the car. Might work but in all probability your main airflow sensor (MAP) is the problem.

sounds like anti theft device has kicked in needs to be reset dont know how to do that though

Battery voltage is definitely and issue. Charge your battery and have it tested before condemning the starter.

2005 CTS 3.6 Dead battery, key stuck, service anti theft and nothing happens when you turn key, Ttried everything, ECM reset, key memory reset, charged battery to 12.7 volts, locked door w remote and opened w key, anyway you get the idea. After 3 days of online reading and trying, THIS IS WHAT WORKED, 1. put key into on position 2. removed sarter relay from front fuse panel 3. jumped 1st pin closest to fender and passenger seat with pin that is closest to motor and front fender. I used a paper clip and just made contact long enough for car to start. ran car for five minutes and took key out and everything went back to normal. then I took car to advance auto parts to have engine light reset. if car does not go back to normal you have ECM (car computer) failure. video on YouTube under "no crank, no start"

You should be able to start, what is the fluid level bring it to the recommended level crank it allow the lifter to solidify and compression will build up

Sounds like an ignition switch problem. Thats one for your mechanic. To get your key out make sure you are in Park (This comes from experience). Good luck.

Test the neutral safety switch by doing the following steps.

1)foot on brake
2)turn key to on position
3)shift lever to neutral (N)
4)start the engine
5)shift the lever to Park (P)

If the engine can start at N and not at park then it's the neutral safety switch.

What is the solution ?