TPMS failure

I had a flat repaired on my 2003 Cadillac Deville and then the TPMS showed no pressure for that tire, but correct pressure for the other three. The tire dealer tried to reprogram the TPMS but couldn’t so I went to a Cadillac dealer. He told me I needed to replace all 4 sensors for $640. Is he ripping me off?

That’s the " if one is bad, the other’s aren’t far behind " logic that your option to buy four or not.
They are battery operated and the battery is built in. All four batteries are the same age and at seven years old one could logic; just how long from now will you need the others ?

But shop around for price. Internet and other GM dealers.
Ask the parts department directly for discounts like a cash discount or a dealership loyalty discount etc.

Paying a labor charge for reprogramming is where you’ll spend extra money if you wait on the other three.

Ever hear the story about how we spent millions to make a pen that would write in the microgravity of space… and the Russians simply issued their cosmonauts pencils!

I hear Russian luxury cars come with a 99 cent tire gauge.