94 Cadillac new ignition took off security still won't start

I hope you have the original ignition key, you'll need it! You have the VATS (Vehicle Anti Theft System) security system. You need to measure the resistance value of the chip on the original ignition key to get the correct VATS key blank. Then using the template key that came with the new lock cylinder have the new key blanks cut. There were 15 possible VATS keys and you can use the chart below to determine which key blank you need. The BCM (Body Control Module) knows which key you should have and if the correct key is not used the BCM will not allow the engine to crank! If you know you have the correct key and the engine still will not crank you need to go into the climate control panel and pull any trouble codes you have stored in the BCM. If you don't know how to do that I can help with that too. If you don't get any trouble codes from the BCM, replace the BCM with a freshly rebuilt one. Do NOT buy a used one. A used BCM will remember which VATS key was needed to start the engine of the vehicle it came out of and you have no idea what key that was. A freshly rebuilt BCM will be "married" to whatever key you use the first time you start the engine with the rebuilt BCM installed. Hope that helps! Jim

Good day to you thanks for answering but you actually told me what I said I have changed I have a new key for my ignition I'm a 40-year mechanic it's just Cadillacs are a bit different especially this one but yeah double checked I got a new relay new starter I mean I put basically everything you on here but then I found out that with a new ignition I still had a security which I had to deal with and I had to do with my locking devices so I found out that if you put your key in the door and you turn it and you hold it for 30 seconds it takes a security off and it did come off but I'm still getting nothing at the starter and it started brand new I haven't left the yard yet thanks for your answer though but that's not the problem right now something else and it's f****** eating me buddy like you wouldn't believe been putting money in his car now for a year and a half anyways thanks

You're welcome. Glad to help! Did you check the BCM for trouble codes? There's also an anti theft relay deep under the dash. Near the bottom of the windshield in the center or near the passenger's side. If this relay goes bad the engine won't crank either. Hope that helps! Jim

I reread your last post. Using the door key won't disable the VATS system so you can start the engine. You need to measure the resistance value of the chip on the original key to determine which VATS key you have. Then you need to order that number blank and use the "dummy" key that came with the new lock cylinder to cut the VATS key to be able to turn the lock cylinder to start the engine. If the BCM is not reading the correct resistance value of the chip on the ignition key it won't allow the starter to crank. You can order the VATS key blank from Ebay or possibly your local GM Dealer. Hope that helps! Jim

Well my friend I had seen those relays behind my glove boxes is like three of them but thanks for letting me know that's one thing I didn't check out of everything thanks again appreciate the time

You're welcome. I went down this road a few years ago with my 94 Fleetwood. After wasting $700 at my local Chevrolet Dealer (the Cadillac Dealer wouldn't go near it, too old) for a misdiagnosis I bought a factory shop manual, did a ton of reading on the security system, and fixed it myself. My BCM was bad. Please keep us posted! I'll be curious to know what the fix is! Jim

Well my friend thanks for answering back well I changed everything from the fuel pump to the coils EGR relays brand new starter new ignition there's so many things I put in this car I'm getting sick of it oh and besides that I got a brand new plug in play ECM for it from RockAuto and I'm still having the same b******* excuse my language

Here's a couple of non security system things to check. Have you checked the neutral safety switch? If it's bad or out of adjustment it will prevent the engine from cranking. Can you jump the neutral safety switch for testing purposes? Same with the ignition switch, at the lower end of the steering column. Will the engine crank if you hook up a temporary remote start button directly between the starter and the battery? I'm assuming when you turn the ignition key all the lights come on and everything but the starter does nothing. Is the engine hydrostaticly locked? Northstar engines are notorious for blowing head gaskets. If one of the cylinders has filled up with coolant the engine will not crank. Liquid can't be compressed. To check this, remove all the spark plugs and try turning the engine by hand. If coolant spurts out of one or more of the spark plug holes, the head gasket is blown and the engine is hydrostaticly locked. Hope that helps! Jim