Question

1995 Cadillac DeVille 4.9L Code p012 4x signal

Answer 1

P012 No 4X reference signal from the ignition control module

Check the terminal connection at the ignition control module, disconnect the connection and reconnect, this method may improve the contact for the ICM to receive and produce the 4X reference signal.

Losing the 4X signal can result in a no-start condition, wiggle the connection to see if you can duplicate the code, if doing so you would have a bad connection rather than a fault with the ignition module