I gotta 2005 cadillac cts and when I try to start

Security light lit or flashing on instrument cluster ?

sounds like the battery is not holding charge and takes a while to recover ,have the battery check at the auto shop usually free if this is ok the starter solenoid may be over heating ,cant think of a way to check this other than new starter

12.3 amps is a bad battery , 500 amps is good, but you meant volts
sure. (by the way sir your battery is discharged, gets forgot?)

12.3 volts rested is a discharged,state ambient temp and can tell by how much using SOC tables.
try jumper cables, try a fully charged battery, 12.6v is fully charged at room temp, rested. barrow a charged battery for friends car.

State of charge.. at room temp.12.3 is 50% charged,
the shops dont tell you that, just GOOD battery, bad,
its your job to charge, it
then when cars starts, the alternator takes over, 100%

the reason you are not going good ,is because no voltmeter in hand. For SURE.
guessing dont work here, only tests and measurements.

1; can you try turning the cars crankshaft by hand.?
siezed, bingo
2: can you hot wire the soleniod small pin to the outside big pin
like here,
http://www.fixkick.com/nocrank.html#test1
if the battery is weak, this test is useless. on all cars.
if it works then the key line is dead
if not the battery ,or cables or starter is bad.
there are 3 parts to a starter,
i repeat, the battery (charged) the cables and the starter.
engine turns by hand. yes.
those are all facts.
another tack.
voltmeter across battery lugs.
crank 0v bad battery or shorted or siezed motor.
12v, starter dead open circuit.
10v typical with fast cranking.
you can see this in 2 dimensions. here.
time is the horizontal axis.
http://www.fixkick.com/Charging/start-voltage-scope.GIF


if living in Nunavut city, cancel my help.
new tables.

Don't do that again! You will need to re-boot the on board computer system by entering a code. Call your nearest Cadillac dealer.

If you need further help, reach me via phone at https://www.6ya.com/expert/lloyd_4256582adacd68ee

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"

A loss of power triggers the Anti theft feature on you car. In some cases, if you lock the drivers door and unlock it with the key, you can reset or rearm the system.

Another method is to turn the key to the On position and leave it there 10 minutes. After 10 minutes, turn the key to attempt to start the car. If these 2 methods don't work, you may need to tow it to the dealer to have the Security reset.

need to reset the anti theft system

My 2003 CTS would not start on the first, second or third try after filling the gas tank. Finally after several months of this occuring every two weeks a check engine light came on. It was the evac purge valve. Tom

it sounds like to me the battery is dead. a way to test that is to trun the headlights on and see if the headlights dim if they do it has a weak charge

Hey Guys! Had the same annoying problem. Cadillac dealer could find nothing wrong with it. Gave me a new battery. Took it to PepBoys and it died for them and immediately they found that it was the Crank Positon Sensor!! Part was $70 + labor. GOOD as NEW!!!!