1. Verify that there is no continuity between antenna feeder terminals A and B using an ohmmeter.

2. Inspect for continuity between the antenna feeder terminals using an ohmmeter.

Front antenna feeder inspectionMazda 6 Service Manual: Cruise Control (Some models)
With cruise control, you can set and automatically maintain any speed of more
than about 25 km/h (16 mph).
WARNING
Do not use the cruise control under the following conditions: Using
the cruise control under the following conditions is dangerous and could result
in loss of vehicle control.
...
Mazda 6 Service Manual: Anchor Bracket
Anchor brackets for securing childrestraint systems are equipped in the vehicle.
Locate each anchor position using the illustration.
To install a child-restraint system, remove the head restraint. Always follow
the instruction manual accompanying the child-restraint system.
Anchor bracket loca ...