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: Intermittent concern troubleshooting
Vibration Method
1. If malfunction occurs or becomes worse while driving on a rough road or
when engine is vibrating, perform the steps below.
Note
There are several reasons vehicle or engine vibration could cause
an electrical malfunction. Some of the things to check for are:
...
Mazda 6 Service Manual: Advisory messages
You'll find several Warnings, Cautions, Notes, Specifications and Upper
and Lower Limits in this manual.
Warning
A Warning indicates a situation in which serious injury or death
could result if the warning is ignored.
Caution
A Caution indicates a situation in which damage to ...