Car shut off while driving will not start

Hi Kathy, welcome to 2CarPros. Let me see what we can do to help.

Lets start simple here and go from there. I need you to check all your fuses in both fuse panels. One under the hood and one in the car. Here is a video link on how to do that:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Next I would like you to plug a scan tool in and see if there are any trouble codes stored in the (PCM) Power train Control Module IE. the computer. Here is a video on how to do that. It is a different vehicle but the procedure is the same for yours.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

https://youtu.be/YV3TRZwer8k

Cadillac also has a feature to retrieve codes without a scan tool. If your car has this feature here is a video on how to do that:

https://youtu.be/UozYykQtg_o

Check these things out and let me know what you find.
Thank you, Rich.

You will not like this if what I am thinking is right. I need you to check the oil. When a motor seizes due to no oil it will get very sluggish as the pistons and bearings melt down. When they seize it will abruptly stop and when you try to start it again the starter slams into the flywheel with a loud click but it can't turn a seized motor over. So check the oil and tell me if there is any at all on the dipstick.

Rich

Okay, this still sounds like it may be seized. Would you be able to put a socket and ratchet on the bolt in the center of the biggest pulley at the bottom of the motor and try to turn the motor by hand? It is also possible the transmission pump has seized which would give all the same symptoms. If the motor or the transmission is seized you wont be able to turn the motor over by hand.

Also please check the transmission fluid.
1. Does it have any.
2. What color is it?
3. Does it smell burnt?
One more note. The dipstick will lie about the color of the fluid so wipe it on a clean white rag or paper towel so you can see the actual color.

Let me know, Rich

Unfortunately it sounds that way. An educated guess would be your timing belt hopped a few teeth, one of the valves hit a piston which broke them both then the broken valve fell down and jammed in the cylinder and locked the motor up. Seized but not, basically.

I am sorry, I wish I had better news for you.

For future reference, Cadillac's love using timing belts and they are all interference motors, which means if the belt breaks or hops a tooth on the timing gear the pistons will hit the valves. I believe they recommend belt replacement every 50,000 miles. Do it every 50,000!

Rich.

You are welcome Kathy and I am sorry, good luck.

Rich