Turn the ignition key to the "ON" position.
Cover the front looking sensor.
Shine a flashlight into the rearward looking sensor.
The mirror should dim as soon as the rearward looking sensor detects the high light level.
If this test is performed in a bright area, the mirror may darken as soon as the front looking sensor is covered.
Put the vehicle into reverse, the mirror should not dim.
Aim a flashlight at the front looking sensor and another flashlight at the rearward looking sensor. The mirror should not darken.
