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: Manual Transaxle Shift Pattern
The shift pattern of the transaxle is conventional, as shown.
Depress the clutch pedal all the way down while shifting; then release it slowly.
Your vehicle is equipped with a device to prevent shifting to R (reverse) by mistake. Push the shift lever downward and shift to R.
...
Mazda 6 Service Manual: Variable tumble control solenoid valve inspection
1. Remove the variable tumble control solenoid valve. (See INTAKE-AIR SYSTEM
REMOVAL/INSTALLATION.)
2. Inspect airflow between the ports under the following conditions.
If not as specified, replace the variable tumble control solenoid valve.
If as specified, carry out the Circuit Open/Short ...