2005 cts battery has full charge will not start when key is turned clicking and battery save mode light is on all other eletrical seems normal

check all your main fuses

Hi
Chances are sticking motor in starter
try tapping the starter motor and re-start the car again.

that will confirm if its defiantly starter

could be something with the automatic combined the stift shift

just get a jump start. if it starts properly. and it has at least 14 volts at battery while running. its a bad battery ! remove negative cable from battery while running. if alternator is not charging battery. engine will quit. if ok, replace or charge battery. good-day !

Take it by a parts store they will test the battery an charging system .

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.

The indicator lights and the neutral safety switch are the same sensor, if one does not work the niether will the other.The mode switch in the transmission needs to be checked and the easiest way to do this is with a scan tool.Seems so simple, i cant imagine why the dealer would not have looked at this.I dont understand why they would install a new computer for a no start condition.

Charge the battery and you may be okey

If you have a backup key, try to disable system by using the key to lock and then un-lock the driver side door. This may work to disable the anti-theft mode. If that doesn't work, disconnect the battery cables then re-correct that normally is the trick. However, make sure it's not your battery. Use the unboard computer and check your battery voltage to make sure it's sufficient to start the car. The key won't eject if the battery is too low to start the car.