B1740 – OBD-II DTC

OBD-II DTC B1740 – Mirror Driver Horizontal Switch Circuit Short To Ground

DTC B1740 meaning

DTC B1740 refers to a diagnostic trouble code indicating a problem with the driver’s side mirror horizontal switch circuit. Specifically, it signifies a short to ground condition in the circuit that controls the horizontal movement of the driver’s side mirror. This issue can prevent the mirror from adjusting properly, affecting visibility and safety while driving.

DTC B1740 symptoms

Common symptoms associated with DTC B1740 may include:

• The driver’s side mirror does not adjust horizontally.
• Intermittent or complete failure of the mirror adjustment function.
• Warning lights or messages on the vehicle’s dashboard.
• Other electrical issues in the vehicle, potentially related to the mirror control system.

DTC B1740 causes

Several factors can lead to the occurrence of DTC B1740, including:

• A short circuit in the wiring harness connected to the mirror switch.
• Faulty mirror switch that may be stuck or damaged.
• Corrosion or poor connections in the electrical connectors.
• Issues with the body control module (BCM) that manages the mirror functions.

DTC B1740 seriousness

The seriousness of DTC B1740 can vary, but it is generally considered a moderate issue. While it may not cause immediate safety concerns, the inability to adjust the driver’s side mirror can lead to reduced visibility, increasing the risk of accidents. It is advisable to address this code promptly to ensure safe driving conditions.

How to diagnose DTC B1740

To diagnose DTC B1740, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the B1740 code.
2. Inspect the mirror switch for physical damage or wear.
3. Check the wiring harness for signs of shorts, fraying, or corrosion.
4. Test the continuity of the wiring between the mirror switch and the mirror motor.
5. Examine the body control module for any faults or error codes.

How to fix DTC B1740 step-by-step instructions

To fix DTC B1740, 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 in the mirror switch circuit.
3. Replace the mirror switch if it is found to be faulty.
4. Reconnect all electrical connections securely.
5. Reconnect the battery and clear the DTC using an OBD-II scanner.
6. Test the mirror adjustment function to ensure it operates correctly.

How to erase DTC B1740

To erase DTC B1740, 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 verify that 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.