B1789 – OBD-II DTC

OBD-II DTC B1789 – Mirror Passenger Down Circuit Short To Ground

DTC B1789 meaning

DTC B1789 refers to a diagnostic trouble code indicating a problem with the passenger side mirror’s down circuit. Specifically, it signifies a short to ground condition in the circuit that controls the downward movement of the passenger side mirror. This code is part of the On-Board Diagnostics II (OBD-II) system, which monitors various vehicle components for faults.

DTC B1789 symptoms

Common symptoms associated with DTC B1789 may include:

• The passenger side mirror does not move down when the control switch is activated.
• Other functions of the passenger side mirror may also be affected.
• Warning lights may illuminate on the dashboard.
• Intermittent or erratic operation of the mirror controls.

DTC B1789 causes

Several factors can lead to the occurrence of DTC B1789, including:

• A short circuit in the wiring harness connected to the passenger side mirror.
• Faulty mirror control switch.
• Defective mirror motor.
• Corrosion or damage in the electrical connectors.
• Issues with the vehicle’s body control module (BCM).

DTC B1789 seriousness

The seriousness of DTC B1789 can vary. While it may not affect the vehicle’s overall drivability, it can hinder the proper adjustment of the passenger side mirror, which is crucial for safe driving. If left unaddressed, it may lead to further electrical issues or damage to the mirror assembly.

How to diagnose DTC B1789

To diagnose DTC B1789, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the B1789 code.
2. Inspect the wiring and connectors related to the passenger side mirror for any visible damage or corrosion.
3. Test the mirror control switch for proper operation.
4. Check the mirror motor for functionality.
5. Examine the body control module for any faults or issues.
6. Perform continuity tests on the wiring to identify any shorts to ground.

How to fix DTC B1789 step-by-step instructions

To fix DTC B1789, follow these step-by-step instructions:

1. Disconnect the vehicle’s battery to ensure safety while working on electrical components.
2. Inspect and repair any damaged wiring or connectors associated with the passenger side mirror.
3. If the mirror control switch is faulty, replace it with a new one.
4. Test and, if necessary, replace the mirror motor.
5. Reconnect all components and ensure proper connections are made.
6. Reconnect the vehicle’s battery.
7. Clear the DTC using an OBD-II scanner and test the mirror operation.

How to erase DTC B1789

To erase DTC B1789, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the vehicle’s ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear DTCs” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the vehicle to ensure the code does not reappear.

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.