The inside rearview mirror uses 2 photocell sensors. One sensor is the rear light sensor, located on the face side of the mirror, facing the rear of the vehicle. The rear light sensor is used to determine light conditions present at the mirror face. The other sensor is the front light sensor, located on the backside of the mirror, facing the front of the vehicle. The front light sensor is used to determine the exterior light conditions at the front of the vehicle. With a low exterior light condition detected by the front light sensor and a high light condition from the rear light sensor, the inside rearview mirror will automatically darken the face of the inside rearview mirror and the left outside rearview mirror. The inside rearview mirror provides a signal circuit and a low reference circuit to the left mirror face to darken the mirror when needed.

With the gear selector lever in the REVERSE position, backup lamp supply voltage is supplied as an input to the inside rearview mirror. The mirror monitors this input to disable the automatic day-night feature. This allows the driver to see objects in the mirror clearly when backing up, regardless of the rear light sensor status.

Schematic Reference

Connector End View Reference

Mirror Connector End Views

Description and Operation

Automatic Day-Night Mirror Description and Operation

Electrical Information Reference

1. Ignition ON, headlamps ON, vehicle in PARK, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor while observing the inside rearview mirror face. The inside rearview mirror face should dim.

⇒	If the mirror face does not dim, test or replace the inside rearview mirror.

2. Headlamps ON, park brake applied, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor while observing the inside rearview mirror face. Place the transmission in REVERSE. The inside rearview mirror face should transition from dim to bright.

⇒	If the mirror does not transition from dim to bright, refer to Reverse Input Malfunction.

3. Headlamps ON, vehicle in PARK, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor while observing the left outside rearview mirror face. The left outside rearview mirror face should dim.

⇒	If the left outside rearview mirror face does not dim, refer to Outside Rearview Mirror Dimming Malfunction.

4. Remove the towel from the inside rearview mirror and remove the flashlight. Verify the inside rearview mirror face returns to its normal bright state.

⇒	If the mirror face does not return to its normal state, test or replace the inside rearview mirror.

Reverse Input Malfunction

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition ON, park brake applied, vehicle in REVERSE, test for B+ between the supply voltage terminal 9 and ground.

⇒	If less than the specified value, test the supply voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, refer to Backup Lamps Malfunction .

3. If all circuits test normal, test or replace the inside rearview mirror.

Outside Rearview Mirror Dimming Malfunction

1. Ignition OFF, disconnect the harness connector C1 at the left outside rearview mirror.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit terminal 6 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, test or replace the inside rearview mirror.

3. Ignition ON, test for less than 1 volt between the signal circuit terminal 5 and ground.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, test or replace the inside rearview mirror.

4. Headlamps ON, vehicle in PARK, cover the front light sensor with a towel or other suitable item. Shine a flashlight at the rear light sensor. Test for greater than 1 volt between the signal circuit terminal 5 and ground.

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the inside rearview mirror.

5. If all circuits test normal, test or replace the left outside rearview mirror face.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.