1. Measure the temperature around the water temperature sensor.
2. Measure the resistance between terminals of the water temperature sensor.

Water temperature sensor removal/installation
Refrigerant pressure switch removal/installationMazda 6 Service Manual: Mazda Radar Cruise Control (MRCC) (Some models)
The Mazda Radar Cruise Control (MRCC) system is designed to maintain headway
control*1 according to the vehicle speed using a radar sensor (front) to detect
the distance to a vehicle ahead, and by presetting the vehicle speed between 30
km/h (19 mph) and 145 km/h (90 mph), the driver is freed ...
Mazda 6 Service Manual: How to use AUX mode
1. Select the icon on the home
screen to display the Entertainment screen.
2. Select to switch to the AUX
mode. The following icons are displayed in the lower part of the center display.
NOTE
If a device is not connected to the auxiliary jack, the mode does not
switch to the AUX mod ...