1. Remove the interlock cable.
2. With the slider pin as shown in the figure, verify that the interlock cable moves freely.

Key interlock inspection
Selector lever inspectionMazda 6 Service Manual: Driving on Uneven Road
Your vehicle's suspension and underbody can be damaged if driven on rough/uneven
roads or over speed bumps at excessive speeds. Use care and reduce speed when traveling
on rough/uneven roads or over speed bumps.
Use care not to damage the vehicle's underbody, bumpers or muffler(s) when driving ...
Mazda 6 Service Manual: Locking, Unlocking the Doors
NOTE
The system may not operate if you are too close to the windows or door
handles.
If the key is left in the following areas and you leave the vehicle,
the doors may be locked depending on the radio wave conditions even if the key
is left in the vehicle.
Around the dashboard
...