The pass key fault light is on and my car wont start

Probably won't pass. The light MUST come on when key is turned to on, or else something is wrong-maybe the engine computer or maybe the wire from pcm to the diagnostic connector or to the dash.
Now I see you say the bulb has voltage? May need to look into possible fault with the pcm.

Videos on you tube showing how to do it . Just search GM anti-theft by pass . There are a few different ones, VATS - pass key - pass - lock , 1 ,2 an 3 .

Get a second ignition key, the one you are using is dirty or moisted, you need to turn on and off the car witha clean key, hapens to me once in a while.!!

Ya, this is a common and potentially expensive problem on GM vehicles like your cadillac. Go to this link for a rundown of how the system works and ways to fix it yourself

http://vatspasslockpasskeysecurityhelp.yolasite.com/

If when you turn the ignition the car lights(in the dash) come on but the car does not crank. the ignition lock cylinder needs to be replaced.

My light stays on

pass key needs replaced also leave ignition on for 30 minutes so pass key around lock cylinder can relearn

i had the same prob in my 94 the ignition cylinder is bad change the ignition and i swear it will work perfect

WELL I HAD THE SAME PROB. ON A 95 CHEVY CAPRICE.I REMOVED THE IGNITION AND THE WIRE WAS BROKE.WHEN U TURN THE KEY THE PASS KEY WIRE TURNS WITH THE IGNITION,WHAT A FAULTY DESIGN.ANY HOW BUY A NEW IGNITION AND KEY THAT SHOULD SOLVE THE PROB. GOOD LUCK

that means than your antitheft system is not operating right,
if your car has a tilt wheel steering system most likelly you need to replace the ignition lock cylinder
this will be also with intermitant wont star simptom