1994 Cadillac Deville Won't start

Is there any messages? HAve you checked the signal at the starter? It could be a faulty or misadjusted park/neutral switch. It could even be a fault with the vehicle theft system, most often the wires break at the ignition cylinder, that are responsible for transmitting the key pellet value to the VATS module. Try starting with the shifter in neutral, inspect the key pellet, if it is worn flat try another key.

If it is a northstar powertrain, there is a large purple wire that goes to a connector at the front of the rear bank of cylinders. This wire is you start signal wire. If you disconnect it and check the harness side with a test light, in the start position it will light if a signal is being sent. You can also power the starter side of it and that would engage the starter. In key on, if you power the starter and it starts and runs, you have a problem with the start circuit.

If it is a 4.9, the signal is the small stud at the starter. You can check it with a test light as well.