WOMS
B code body Medium severity

B1786 Mirror Passenger Down Circuit Failure

The OBD2 code B1786 indicates a failure in the passenger side mirror's down circuit, meaning there is a malfunction preventing the mirror from moving down as intended

Definition

The OBD2 code B1786 indicates a failure in the passenger side mirror's down circuit, meaning there is a malfunction preventing the mirror from moving down as intended

Common causes

  • Faulty passenger side mirror switch
  • Damaged wiring or connectors in the mirror circuit
  • Defective passenger side mirror motor
  • Short circuit in the mirror down circuit
  • Blown fuse related to the mirror system
  • Corrosion or poor connections in the wiring harness
  • Malfunctioning body control module (BCM)

Common misdiagnoses

  • Faulty window switch
  • Wiring issues or shorts
  • Defective power window motor
  • Malfunctioning body control module (BCM)
  • Incorrectly installed or damaged door panel
  • Issues with the driver's side window control
  • Faulty relay or fuse related to window operation

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple issues

  2. 2. Inspect the Wiring and Connectors

    Visually inspect the wiring harness and connectors associated with the passenger side mirror. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the wires that control the mirror's movement

  4. 4. Test the Mirror Switch

    The mirror control switch may be faulty. Test the switch for continuity using a multimeter. If the switch is not functioning properly, it may need to be replaced

  5. 5. Check the Power Supply

    Ensure that the mirror is receiving power. Use a multimeter to check for voltage at the mirror connector when the switch is activated

  6. 6. If there is no power, trace the circuit back to the fuse box and check for blown fuses or faulty relays

  7. 7. Inspect the Mirror Motor

    The mirror motor itself may be defective. If possible, test the motor by applying direct power to it to see if it operates. If it does not move, the motor may need to be replaced

  8. 8. Check for Ground Issues

    Ensure that the ground connection for the mirror circuit is secure and free of corrosion. A poor ground can cause various electrical issues

  9. 9. Look for Short Circuits

    Inspect the circuit for any signs of short circuits. This can occur if wires are pinched or damaged, causing them to touch each other or the vehicle chassis

  10. 10. Consult Wiring Diagrams

    Refer to the vehicle’s service manual for wiring diagrams specific to the mirror circuit. This can help you understand the circuit layout and identify potential problem areas

  11. 11. Perform a System Reset

    Sometimes, clearing the code and resetting the system can resolve temporary glitches. Use the OBD-II scanner to clear the code and see if it returns

  12. 12. Seek Professional Help

    If the issue persists after performing these steps, it may be best to consult a professional mechanic or an automotive electrician for further diagnosis and repair. By following these troubleshooting steps, you should be able to identify the cause of the B1786 code and take appropriate action to resolve the issue