Caddie wont turn over

Is there a message on the info center stating theft system problem? Check for the presence of a signal at the starter solenoid 'S' terminal(purple wire). If there is no start signal, it would be safe to presume the ignition cylinder may be faulty. You would have to remove the lower i/p insulator under the drivers side, to access the wiring for the ignition cylinder, it is most commonly two very small wires in an orange conduit. With it disconnected, check the resistance across the two wires with the key in the ignition, and rotated to all positions. You should have a resistance value, somewhere around 1000 ohms(it may vary), and it should be the same in all positions. If it goes higher, or open circuit, you have a fault in the cylinder which is usually broken wires up in the column.

If the security lite is off. Hold in crank position and use a hammer to tap the starter. If it starts the starter is bad if not go to the purple wire on the ingition switch on top of the lower steering column. Check the voltage on the purple wire. If this alarm isnt factory installed. Find the alarm module and hook up the starter wire for testing. You can use a multi meter to read the key chip. Then insert the key in the ingition. Go to the base of the steering column. Youll see a orange harness with 2 white wires. Read ohms over the 2 white wires it should read the same as the key chip reads. If the ohms are differant u need a new key cylinder. You can trick it if the chip reads 1200 ohms go to radio shack and buy a 1200 resister. Then unplug the orange harness install the resister on the body harness across the 2 white wires. This by passes the passkey though untill you repair it. Gl