you got the wrong key.
Majority of the time the problem is in the ignition key chip or ignition lock cylinder
The wires on the lock cylinder are broken-needs new lock cylinder./
To disarm the factor alarm on a Cadillac Sedan Deville, place the key in the ignition and turn it slightly without starting the car. Leave it in that position for 10 minutes and turn the car on.
You can reset the theft system in your 1994 Cadillac Deville by putting the key into the ignition. Turn the ignition to the auxiliary position, without starting the engine. Leave it in this position for 30 seconds.
Ignition Key switch is bad.
Won't the valet key open the trunk
1. it's the wrong key 2. your Ex busted something in the cylinder such as part of the wrong key 3. one of the tumbler's is bent out solution call a locksmith
By turning the ignition key
willnot open trunk or locked compartments
cant its the computer
Press the trunk button on the dash board or the remote key fob
make sure everything is off (radio, etc). place your key in the ignition, half turned on, for 20 min or so and that will reset the security system. i had to do this with my 2000 deville and it worked. try it at your own risk. goodluck