Hyundai Elantra: Electro Chromic Inside Rear View Mirror / Description and operation
The ECM (Electro Chromatic inside rear view Mirror) is intended dim the reflecting light in the rear view mirror. The forward facing sensor detects brightness of the surroundings, while the rearward looking sensor is for the light from the rear. The strength of the light in the rear sensor is used by the mirror to adjust the shading. It ranges from 7 to 85%. When the reverse gear is engaged, it stops functioning.
| 1. | The forward facing sensor sees if the brightness of the surroundings is low enough for the mirror to operate its function. |
| 2. | The rearward looking sensor detects glaring of the reflecting light from a vehicle behind. |
| 3. | The ECM is darkened to the level as determined by the rearward looking sensor. When the glaring is no longer detected, the mirror stops functioning. 

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| Automatic-dimming Function |
To protect your vision during nighttime driving, your mirror will automatically dim upon detecting glare from the vehicles traveling behind you. The auto-dimming function can be controlled by the Dimming ON/OFF Button :
| 1. | Pressing and holding the Feature Control button for more than 3 but less than 6 seconds turns the auto-dimming function OFF which is indicated by the green Status Indicator LED turning off. |
| 2. | Pressing and holding the Feature Control button again for more than 3 but less than 6 seconds turns the auto-dimming function ON which is indicated by the green Status Indicator LED turning on. | •
| The mirror defaults to the "ON" position each time the vehicle is started. |
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Other information:
Components and components location
Components
Repair procedures
Removal1.Disconnect the negative (-) battery terminal.2.Remove the driver door trim.(Refer to Body - "Front Door Trim")3.Remove the memory power switch (A) after disengaging the mounting clips.Installation1.Install the memory power seat control switch (IMS).2.Install the door trim.3.Connect the negative (-) battery termina..
Components1. Cowl side trim 2. Front door scuff trim 3. Rear door scuff trim 4. Front pillar trim 5. Center pillar upper trim 6. Center pillar lower trim 7. Rear pillar trim ..