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

Cabin temperature sensor removal/installation
Evaporator temperature sensor removal/installationMazda 6 Service Manual: Starting the Engine
WARNING
Radio waves from the key may affect medical devices such as pacemakers:
Before using the key near people who use medical devices, ask the medical device
manufacturer or your physician if radio waves from the key will affect the device.
NOTE
The key must be carried because the key c ...
Mazda 6 Service Manual: Automatic Transaxle Controls
Various Lockouts:
Indicates that you must depress the brake
pedal and hold in the lock-release button to shift (The ignition must be switched
ON).
Indicates the shift lever can be shifted
freely into any position.
Indicates that you must hold in the lock-release
button to shift.
N ...