B1787 – OBD-II DTC

OBD-II DTC B1787 – Mirror Passenger Down Circuit Open

DTC B1787 meaning

DTC B1787 refers to a diagnostic trouble code indicating an issue with the passenger side mirror’s down circuit. This code is triggered when the vehicle’s onboard diagnostic system detects an open circuit in the wiring or components responsible for controlling the downward movement of the passenger side mirror. An open circuit means that there is a break in the electrical path, preventing the mirror from functioning as intended.

DTC B1787 symptoms

Common symptoms associated with DTC B1787 may include:

• The passenger side mirror does not move down when the control switch is activated.
• Other mirror functions (up, left, right) may still work, indicating a localized issue.
• Possible warning lights on the dashboard related to the mirror or electrical system.
• Intermittent operation of the mirror, where it may work occasionally but not consistently.

DTC B1787 causes

Several factors can lead to the triggering of DTC B1787, including:

• A broken or damaged wire in the mirror control circuit.
• A faulty mirror switch that fails to send the correct signal.
• Corrosion or poor connections at the wiring harness or connectors.
• A malfunctioning mirror motor that cannot respond to commands.
• Issues with the vehicle’s body control module (BCM) that may affect mirror operations.

DTC B1787 seriousness

The seriousness of DTC B1787 can vary. While it may not pose an immediate safety risk, it can affect the driver’s ability to adjust the passenger side mirror, which is important for safe driving. If left unaddressed, it could lead to further electrical issues or complications with other systems in the vehicle.

How to diagnose DTC B1787

To diagnose DTC B1787, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B1787.
2. Inspect the wiring and connectors related to the passenger side mirror for any visible damage or corrosion.
3. Test the mirror switch for proper operation using a multimeter.
4. Check the mirror motor by applying direct power to see if it functions.
5. Examine the body control module for any faults or issues that may affect mirror operation.

How to fix DTC B1787 step-by-step instructions

To fix DTC B1787, follow these steps:

1. Identify and repair any damaged wiring or connectors in the mirror control circuit.
2. Replace the mirror switch if it is found to be faulty.
3. Test and replace the mirror motor if it does not respond to direct power.
4. Clear any corrosion from connectors and ensure all connections are secure.
5. Recheck the system with an OBD-II scanner to ensure the code has been resolved.

How to erase DTC B1787

To erase DTC B1787, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Access the trouble codes menu on the scanner.
3. Select the option to clear or erase trouble codes.
4. Confirm the action and wait for the scanner to complete the process.
5. Disconnect the scanner and take the vehicle for a test drive to ensure the code does not return.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.