Buick Regal: Automatic Day-Night Mirrors Malfunction

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

1. Inside and Outside Rearview Mirror Automatic Dimming Malfunction
2. Outside Rearview Mirror Automatic Dimming Malfunction

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 and the driver outside rearview mirror. The inside rearview mirror provides a signal circuit and a low reference circuit to the driver mirror face to darken the mirror when needed.

With the gear selector lever in the REVERSE position and the engine running, backup lamp control 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 Wiring Schematics
• Outside Rearview Mirror Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

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

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON.

2. Cover the windshield with a blanket or other suitable item.

3. Verify the A10 Inside Rearview Mirror face dims when shining a bright light into the rear light sensor

• If the A10 Inside Rearview Mirror does not dim

Refer to Circuit/System Testing - Inside Review Mirror Dimming Inoperative

• Go to next step: If the A10 Inside Rearview Mirror dims

4. Verify the A10 Inside Rearview Mirror face transitions from dim to bright while commanding the Backup Lamps Active and Inactive with a scan tool.

• If the A10 Inside Rearview Mirror does not transition between dim and bright.

Refer to Circuit/System Testing - Day-Night Disable Malfunction

• Go to next step: If the A10 Inside Rearview Mirror transitions between bright and dim states

5. Verify the A9A Outside Rearview Mirror-Driver face dims when shining a bright light into the rear light sensor.

• If the A9A Outside Rearview Mirror-Driver does not dim

Refer to Outside Rearview Mirror Dimming Malfunction.

• Go to next step: If the A9A Outside Rearview Mirror-Driver dims

6. Verify the A9A Outside Rearview Mirror-Driver face transitions from dim to bright while commanding the Backup Lamps Active and Inactive with a scan tool.

• If the A9A Outside Rearview Mirror-Driver does not transition between bright and dim states

Refer to Outside Rearview Mirror Dimming Malfunction.

• Go to next step: If the A9A Outside Rearview Mirror-Driver transitions between bright and dim states

7. All OK.

Circuit/System Testing

Inside Review Mirror Dimming Inoperative

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the A10 Inside Rearview Mirror. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 5 and ground.

• If 10 Ω or greater

1. Ignition OFF, remove the test lamp.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Verify a test lamp illuminates between the ignition circuit terminal 2 and ground.

If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the test lamp.
2. Test for less than 2 Ω in the ignition circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the ignition circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the A10 Inside Rearview Mirror

• Go to next step: If the test lamp illuminates

5. Replace the A10 Inside Rearview Mirror.

Day-Night Disable Malfunction

1. Ignition OFF, disconnect the harness connector at the A10 Inside Rearview Mirror. Ignition ON 2. Connect a test lamp between the control circuit terminal 1 and ground 3. Verify the test lamp turns ON and OFF while commanding the Backup Lamps Active and Inactive with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit terminal 1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, refer to Backup Lamps Malfunction.

• If the test lamp is always ON

1. Ignition OFF, remove the test lamp, disconnect the harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, refer to Backup Lamps Malfunction

• Go to next step: If the test lamp turns ON and OFF

4. Replace the A10 Inside Rearview Mirror.

Outside Rearview Mirror Dimming Malfunction

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the A9A Outside Rearview Mirror-Driver. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 10 Ω between the low reference circuit terminal 16 and ground.

• If 10 Ω or greater

1. Ignition OFF, disconnect the harness connector at the A10 Inside Rearview Mirror.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the A10 Inside Rearview Mirror.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Test for less than 1 V between the control circuit terminal 2 and ground.

• If 1 V or greater

1. Ignition OFF, disconnect the harness connector at the A10 Inside Rearview Mirror, ignition ON.
2. Test for less than 1 V between the control circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V replace the A10 Inside Rearview Mirror.

• Go to next step: If less than 1 V

5. 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.

6. Test for greater than 1 V between the control circuit terminal 2 and ground.

• If 1 V or less

1. Ignition OFF, disconnect the harness connector at the A10 Inside Rearview Mirror, ignition ON.
2. Test for infinite resistance between the control circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, test or replace the A10 Inside Rearview Mirror.

• Go to next step: If greater than 1 V

7. Test or replace A9A Outside Rearview Mirror-Driver.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Inside Rearview Mirror Replacement
• Outside Rearview Mirror Glass Replacement

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