Your post touches two points worth to think about:

The test for consciousness: if we do have zero criterion, how we are gonna find out if something is conscious?

That is already a good indicator how much we do not know about the „mechanism” of consciousness.

Point two is that we in fact know so little, that we cannot even nail a probability for some complex mechanism if is conscious.

A car: probably not, too far away from things that are conscious.

An ant?

A microphone that listens to its output?

A k-means run on some data?

An llm?

Some electricity in a biological neural network?

If only we had a proven criterion to decide!