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