B1721 – Seat Driver Rearward Switch Circuit Failure

The ODBII code B1721 indicates a malfunction in the driver rearward seat switch circuit, which may involve issues with the switch itself, wiring, or the seat control module.

The severity of ODBII code B1721 is generally considered moderate.

Common Causes For: B1720 Seat Driver Forward Switch Circuit Short To Ground

• Faulty seat driver rearward switch
• Damaged wiring or connectors in the switch circuit
• Short circuit in the wiring harness
• Open circuit in the wiring harness
• Corrosion or poor connections at the switch or connector
• Malfunctioning power seat control module
• Grounding issues in the circuit

Common misdiagnosis for B1721 Seat Driver Rearward Switch Circuit Failure

• Faulty seat switch
• Wiring issues or shorts in the circuit
• Malfunctioning body control module (BCM)
• Incorrectly diagnosed seat position sensor
• Issues with the power supply or ground connections
• Faulty connectors or terminals
• Problems with the seat motor or actuator

Common Troubleshooting Steps

The OBD-II code B1721 indicates a problem with the driver rearward seat switch circuit. This code is typically associated with issues in the seat adjustment system, particularly the switch that controls the rearward movement of the driver’s seat. Here are some common troubleshooting steps to diagnose and potentially resolve the issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple issues.
• Inspect the Seat Switch:
• Remove the seat switch from the driver’s seat.
• Check for any visible damage, corrosion, or loose connections.
• Test the switch for continuity using a multimeter. If the switch is faulty, it may need to be replaced.
• Examine Wiring and Connectors:
• Inspect the wiring harness and connectors leading to the seat switch and the seat motor.
• Look for frayed wires, broken connections, or signs of wear and tear.
• Repair or replace any damaged wiring or connectors.
• Test the Seat Motor:
• If the switch appears to be functioning correctly, test the seat motor itself.
• Apply direct power to the motor to see if it operates. If it does not, the motor may be faulty and require replacement.
• Check for Ground Issues:
• Ensure that the seat motor and switch have a good ground connection. A poor ground can cause circuit failures.
• Use a multimeter to check for continuity to ground.
• Inspect the Body Control Module (BCM):
• In some vehicles, the BCM controls the seat functions. If all other components check out, the BCM may be malfunctioning.
• Check for any software updates or recalls related to the BCM.
• Clear the Code and Test Drive:
• After performing repairs, clear the trouble code using the OBD-II scanner.
• Take the vehicle for a test drive to see if the code reappears.
• Consult the Vehicle’s Service Manual:
• Refer to the specific service manual for your vehicle for detailed wiring diagrams and troubleshooting procedures.
• Seek Professional Help:
• If the issue persists after performing these steps, it may be best to consult a professional mechanic or an automotive technician for further diagnosis. By following these steps, you should be able to identify and resolve the issue related to the B1721 code.