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: Engine Exhaust (Carbon monoxide)
WARNING
Do not drive your vehicle if you smell exhaust gas inside the vehicle:
Engine exhaust gas is dangerous. This gas contains carbon monoxide (CO), which is
colorless, odorless, and poisonous. When inhaled, it can cause loss of consciousness
and death. If you smell exhaust gas inside the ...
Mazda 6 Service Manual: Obd drive mode
Performing the Drive Mode inspects the OBD system for proper operation.
The Drive Mode must be performed to ensure that no additional DTCs are
present.
During Drive Mode, the following systems are inspected:
- Oxygen sensor (HO2S)
- Oxygen sensor heater
- Catalytic converter (TW ...