What to check

Disconnect the co-axial cable from the camera in the door panel and check the resistance across the core and screen which should be about 75 ohms.

Corrective Action

Ensure that the co-axial cable conductors are securely fastened at the terminals at both ends of the cable and that the wire or screening braid is not shorting to other terminals or PCB tracks in the splitter or telephone.

Consider replacing the section of co-axial cable if all other checks fail and you have no continuity on coax