Thank you again.

The sensor ID is correct. I have tested the same sensor and the same piece of code with 16F876A using PortC.0, and I can read the sensor without any trouble. Hardware is ok, checked it carefully. Again my opinion is, that something is wrong with my code with GPIO.1. I am not an engineer, and I am not sure how these pins work in 12F508. When using 16F876A or 16F873 no special configuration is needeed. Just define:

DQ var PortC.0

and everything works.