B1721 – OBD-II DTC

OBD-II DTC B1721 – Seat Driver Rearward Switch Circuit Failure

DTC B1721 meaning

DTC B1721 refers to a fault in the seat driver rearward switch circuit. This diagnostic trouble code indicates that the vehicle’s onboard diagnostic system has detected an issue with the electrical circuit responsible for the rearward movement of the driver’s seat. The problem may stem from a malfunctioning switch, wiring issues, or a failure in the seat control module.

DTC B1721 symptoms

Common symptoms associated with DTC B1721 may include:

• The driver’s seat not moving rearward when the switch is activated.
• Intermittent or complete failure of the seat adjustment function.
• Illumination of the airbag warning light on the dashboard.
• Other seat adjustment functions may also be affected.

DTC B1721 causes

Several factors can lead to the occurrence of DTC B1721, including:

• A faulty seat driver rearward switch.
• Damaged or frayed wiring in the seat adjustment circuit.
• Corrosion or poor connections in the electrical connectors.
• Malfunctioning seat control module.
• Issues with the vehicle’s body control module (BCM) affecting seat functions.

DTC B1721 seriousness

DTC B1721 is considered a moderate issue. While it may not affect the vehicle’s drivability, it can impact the comfort and safety of the driver. If the seat cannot be adjusted properly, it may lead to improper driving posture, which can increase the risk of injury in the event of an accident. Additionally, the illumination of the airbag warning light indicates that there may be a related issue with the airbag system, which is a critical safety concern.

How to diagnose DTC B1721

To diagnose DTC B1721, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B1721.
2. Inspect the seat driver rearward switch for physical damage or wear.
3. Check the wiring and connectors for signs of corrosion, damage, or loose connections.
4. Test the seat driver rearward switch using a multimeter to ensure it is functioning correctly.
5. Examine the seat control module for any fault codes or issues.
6. Perform a continuity test on the wiring harness to ensure there are no breaks in the circuit.

How to fix DTC B1721 step-by-step instructions

To fix DTC B1721, follow these steps:

1. Disconnect the vehicle’s battery to ensure safety while working on the electrical system.
2. Inspect and replace the seat driver rearward switch if it is found to be faulty.
3. Repair or replace any damaged wiring or connectors in the seat adjustment circuit.
4. Clean any corroded connections to ensure good electrical contact.
5. Reinstall the seat control module if it was removed for testing, ensuring all connections are secure.
6. Reconnect the vehicle’s battery and clear the DTC using an OBD-II scanner.
7. Test the seat adjustment functions to ensure they are operating correctly.

How to erase DTC B1721

To erase DTC B1721, 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. Follow the prompts to clear the trouble codes from the vehicle’s memory.
5. Disconnect the scanner and turn off the ignition.
6. Start the vehicle and check if the DTC reappears after a test drive.

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