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: Rear Cross Traffic Alert (RCTA) (Some models)
The Rear Cross Traffic Alert (RCTA) system is designed to assist the driver in
checking the area to the rear of the vehicle on both sides while the vehicle is
reversing by alerting the driver to the presence of vehicles approaching the rear
of the vehicle.
The Rear Cross Traffic Alert (RCTA) ...
Mazda 6 Service Manual: A/c unit removal/installation
1. Disconnect the negative battery cable.
2. Discharge the refrigerant from the system. (See RECOVERY.) (See CHARGING.)
3. Drain the engine coolant. (See ENGINE COOLANT REPLACEMENT.)
4. Remove the dashboard. (See DASHBOARD REMOVAL/INSTALLATION.)
5. Remove the theft-deterrent control module. (See ...