WOMS
B code body Medium severity

B1778 Mirror Driver Down Circuit Failure

The OBD2 code B1778 indicates a failure in the mirror driver down circuit, which typically relates to the malfunction of the power mirror's downward movement function in a vehicle

Definition

The OBD2 code B1778 indicates a failure in the mirror driver down circuit, which typically relates to the malfunction of the power mirror's downward movement function in a vehicle

Common causes

  • Faulty mirror driver module
  • Damaged wiring or connectors
  • Short circuit in the mirror driver circuit
  • Open circuit in the mirror driver circuit
  • Corroded or loose connections
  • Malfunctioning power supply to the mirror driver
  • Software or programming issues in the vehicle's control module

Common misdiagnoses

  • Faulty mirror switch
  • Wiring issues or shorts in the mirror circuit
  • Defective power mirror motor
  • Malfunctioning body control module (BCM)
  • Incorrectly diagnosed window regulator issues
  • Problems with the vehicle's electrical system or battery
  • Software or programming errors in the vehicle's computer systems

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 Wiring and Connectors

    Visual Inspection: Check the wiring harness and connectors associated with the mirror assembly for any signs of damage, corrosion, or loose connections

  3. 3. Continuity Test

    Use a multimeter to test for continuity in the wiring. Look for breaks or shorts in the circuit

  4. 4. Test the Mirror Assembly

    Functionality Test: Manually operate the mirror controls to see if the mirror adjusts properly. If it does not, the mirror assembly may be faulty

  5. 5. Power Supply Check

    Verify that the mirror is receiving power. You can do this by checking the voltage at the mirror connector with a multimeter

  6. 6. Inspect the Mirror Control Switch

    Check the mirror control switch for proper operation. If the switch is faulty, it may not send the correct signals to the mirror assembly

  7. 7. Check for Ground Issues

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

  8. 8. Examine the Body Control Module (BCM)

    The BCM often controls the power mirrors. Check for any faults in the BCM and ensure it is functioning correctly. If necessary, reprogram or replace the BCM

  9. 9. Look for Software Updates

    Check if there are any software updates available for the vehicle's control modules. Sometimes, manufacturers release updates to fix known issues

  10. 10. Perform a Reset

    Clear the trouble codes using the OBD-II scanner and see if the code returns after a test drive. This can help determine if the issue is intermittent

  11. 11. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the B1778 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations

  12. 12. Professional Diagnosis

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose the problem accurately. By following these steps, you should be able to identify and potentially resolve the issue related to the B1778 code. Always refer to the vehicle's service manual for specific procedures and specifications