For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | 2 | 2 | -- | --
Backup Lamp Supply Voltage | 1 | 1 | 2 | --
Ground | -- | 2 | 2 | --
1. Rearview mirror remains dimmed in reverse 2. Rearview mirror does not dim

### Circuit/System Description

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.

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.

### Reference Information

#### Schematic Reference

Inside Rearview Mirror Schematics

#### Connector End View Reference

Mirror Connector End Views

#### Description and Operation

Automatic Day-Night Mirror Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Verification

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, refer to Inside Rearview Mirror Circuit Malfunction.

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. 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.

### Circuit/System Testing

#### Inside Rearview Mirror Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal 8 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 13 and ground.

⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, 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 circuit 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 Inoperative .

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Inside Rearview Mirror Replacement