Car was running great, heater core started leaking real bad, changed it, now the car will not start. I dont believe it is a security issue, have rechecked all connections that were undone during heater core change, they all seem to be okay.
The car does the same thing when PCM is plugged in, and when it was unplugged.

 

If security light stays on, good chance. Codes? ECM is near heater core access..could coolant leaked into it?

 

No, the security light goes off, that is why I don't think that is the problem. As for the water leaking into PCM, that is a possibility. The car was running up to the heater core going out, however there was water all over the inside of the car.
Codes? Yes, it had some codes, I left the list in the car. Will get back to you tomorrow with them. And thank you for your help.

 

So, I have my car running now. Is it fixed? Not yet. Why does everyone run the other way when you mention them working on a Cadillac? My car has 295,700 miles on it, and at this point I believe it will go that many more, provided I find a mechanic to fix it when things go wrong. I have been very fortunate with this car, the normal repairs such as brakes, tires, oil changes, alternator and a brand new air conditioner compressor are all the repairs that this car has had until now. And until now my father fixed it, changed oil, rotated tires....he did it all for me. Unfortunately, he was taken from us unexpectedly in March.

So, back to my car and the fact that I can get it started and drive it. To start it, I sit in the passenger floorboard, turn the key in the ignition with my left hand.....while wiggling a wiring harness with my right. When I learned this would start it I was still afraid to drive it, because I thought if I hit a bump in the road it would die, but my son took my other car out of town last weekend, so it was either drive it or stay home. I drove it all over. Never died once. Sometimes it starts without moving the wires, but not always. I know this can not be good for the starter or the ignition, I have narrowed it down to a clip with about 20 wires in it, but I don't know how to test them.

You might think this car is not worth the trouble due to the mileage, but it is in excellent shape. Looks brand new on the outside, and a new drivers seat would make the interior look really good to.

If you can't talk me thru the wiring problem, maybe a decent mechanic in NW Tennessee could leave me the name of his shop so I can take it to get it fixed.

 

Disconnect connector and see what terminals look like. If you have some electrical contact cleaner spray it, let it dry, and reconnect connector. See what happens. If you still have trouble, you can try to wiggle the different wires to try to isolate fault wire(s).

 

If you can get a pic of the connector and post it, we might be able to narrow down the possibilities, but I agree with slowroll on dis-connecting it, and checking/cleaning the terminals. Look for any green/whiteish funk, or blackened terminals.
It's also possible one(or more) of the terminals is loose on the actual wire, and may need crimping, or re-sizing.