B1785 – Mirror Passenger Up Circuit Short To Ground

The ODBII code B1785 indicates a fault in the passenger side mirror’s “up” movement circuit, specifically a short to ground, which means there is an unintended connection to the vehicle’s ground, preventing the mirror from functioning properly.

The severity of ODBII code B1785 is generally considered moderate.

Common Causes For: B1784 Mirror Passenger Up Circuit Short To Battery

• Damaged wiring or connectors in the mirror circuit.
• Shorted or faulty mirror switch.
• Malfunctioning power mirror motor.
• Corroded or loose electrical connections.
• Faulty body control module (BCM).
• Water intrusion or moisture in the electrical components.

Common misdiagnosis for B1785 Mirror Passenger Up Circuit Short To Ground

• Faulty passenger side mirror switch
• Damaged wiring harness
• Shorted wiring in the door panel
• Defective body control module (BCM)
• Malfunctioning power window switch
• Incorrectly installed or faulty mirror assembly
• Issues with the vehicle’s electrical system or grounding points

Common Troubleshooting Steps

The OBD-II code B1785 indicates a problem with the passenger side mirror’s “up” circuit, specifically a short to ground. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Visual Inspection:
• Check the wiring harness and connectors associated with the passenger side mirror. Look for any signs of damage, fraying, or corrosion.
• Inspect the mirror assembly for any physical damage that could affect the wiring.
• Check for Shorts:
• Use a multimeter to check for continuity in the wiring. Disconnect the mirror connector and test the wires for continuity to ground. If you find continuity, there may be a short in the wiring.
• Inspect the wiring for any areas where it may be pinched or rubbing against metal surfaces.
• Test the Mirror Motor:
• If the wiring appears intact, test the mirror motor itself. You can do this by applying direct power to the motor to see if it operates correctly.
• If the motor does not work when powered directly, it may need to be replaced.
• Check the Switch:
• Inspect the mirror control switch for proper operation. A faulty switch can cause incorrect signals to be sent to the mirror motor.
• Test the switch for continuity and proper function. If it’s defective, replace it.
• Scan for Additional Codes:
• Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues.
• Inspect Ground Connections:
• Ensure that all ground connections related to the mirror and the control circuit are clean and secure. A poor ground can cause erratic behavior and false codes.
• Check for Water Intrusion:
• Water can sometimes enter the mirror assembly or wiring harness, causing shorts. Inspect for any signs of moisture or corrosion.
• Repair or Replace Components:
• Based on your findings, repair any damaged wiring or connectors. If the mirror motor or switch is faulty, replace them as necessary.
• Clear Codes and Test Drive:
• After making repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Service Manual:
• If the issue persists, consult the vehicle’s service manual for specific wiring diagrams and troubleshooting procedures related to the mirror circuit. By following these steps, you should be able to identify and resolve the issue causing the B1785 code. If you’re not comfortable performing these diagnostics, consider seeking assistance from a professional mechanic.