WOMS
B code body Medium severity

B1787 Mirror Passenger Down Circuit Open

The OBD2 code B1787 indicates that there is an open circuit in the passenger side mirror's down movement function, meaning the system is unable to detect or control the downward movement of the passenger side mirror

Definition

The OBD2 code B1787 indicates that there is an open circuit in the passenger side mirror's down movement function, meaning the system is unable to detect or control the downward movement of the passenger side mirror

Common causes

  • Faulty passenger side mirror switch
  • Damaged wiring or connectors in the mirror circuit
  • Failed passenger side mirror motor
  • Blown fuse related to the mirror circuit
  • Poor ground connection for the mirror system
  • Corrosion or dirt in the connector terminals

Common misdiagnoses

  • Faulty window switch
  • Broken wiring or connectors
  • 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 the Vehicle's Manual

    Refer to the vehicle's service manual for specific information about the mirror circuit and wiring diagrams

  2. 2. Visual Inspection

  3. 3. Inspect the wiring harness and connectors leading to the passenger side mirror for any signs of damage, corrosion, or loose connections

  4. 4. Look for any frayed wires or broken connectors that could cause an open circuit

  5. 5. Test the Mirror Switch

  6. 6. Use a multimeter to test the mirror control switch. Ensure that it is functioning correctly and sending the appropriate signals to the mirror

  7. 7. If the switch is faulty, it may need to be replaced

  8. 8. Check the Mirror Motor

  9. 9. Test the passenger side mirror motor by applying direct power to it. If the motor does not respond, it may be defective and require replacement

  10. 10. Inspect Fuses

  11. 11. Check the fuses related to the power mirrors. A blown fuse could interrupt the circuit and cause the code to trigger

  12. 12. Scan for Additional Codes

  13. 13. Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues

  14. 14. Check Ground Connections

  15. 15. Ensure that the ground connections for the mirror circuit are secure and free of corrosion. A poor ground can lead to circuit issues

  16. 16. Perform a Continuity Test

  17. 17. Use a multimeter to perform a continuity test on the wiring from the mirror switch to the mirror motor. This will help identify any breaks in the circuit

  18. 18. Inspect the Body Control Module (BCM)

  19. 19. If all other components check out, the issue may lie within the BCM. Ensure that it is functioning correctly and that there are no software issues

  20. 20. Clear the Code and Test Drive

  21. 21. After performing repairs or replacements, clear the trouble code using an OBD-II scanner and take the vehicle for a test drive to see if the code returns. If you are not comfortable performing these steps or if the issue persists after troubleshooting, it may be best to consult a professional mechanic for further diagnosis and repair