B1673 — Seat Driver Occupied Input Circuit Open #

Note: The description of DTC B1673 may vary depending on the vehicle manufacturer (OEM). Always refer to your vehicle’s official service documentation for the most accurate definition.

• Seat Driver Occupied Input Circuit Open (Ford, Lincoln, Mercury)
• Driver Seat Occupancy Sensor Input Open Circuit (Toyota, Lexus)
• Driver Presence Detection Circuit Open (GM, Chevrolet, Cadillac)

Summary of DTC B1673 #

Diagnostic Trouble Code B1673 indicates an open circuit in the driver’s seat occupancy input. This circuit is responsible for detecting whether the driver’s seat is occupied, primarily through a weight sensor or seat pressure mat. The signal from this system is vital for features like airbag deployment logic, seatbelt reminders, and other occupant safety technologies. When this code is triggered, it means the control module senses a break or interruption in the circuit. Prompt diagnosis is important, as improper occupant detection can compromise passive safety features.

Common Symptoms for Code B1673 #

When your vehicle registers B1673, you may notice telltale signs, but sometimes the symptoms are subtle enough to go unnoticed until an inspection or a warning light appears. The most obvious symptom is usually a warning light on the dashboard, but other occupant-related functions may also behave abnormally.

• Airbag or SRS (Supplemental Restraint System) warning light illuminated
• Seatbelt reminder chime not working as intended
• Airbag deactivation indicator on when seat is occupied
• Occupant classification system not registering driver presence
• Possible trouble with seat memory or power features (less common)

Likely Causes for Code B1673 #

Several potential issues can result in an open circuit for the driver’s seat occupancy input. The following are listed in order of most to least common, based on typical field diagnostics and OEM documentation.

1. Faulty seat occupancy sensor (weight sensor or mat)
2. Damaged or disconnected wiring harness under the driver’s seat
3. Poor or corroded electrical connectors at the seat or module
4. Faulty occupant detection module
5. Blown fuse related to occupant detection or airbag circuit
6. Incorrectly installed aftermarket equipment (e.g., seat covers interfering with sensor)

Step-by-Step Diagnosis for Code B1673 #

A careful, systematic approach is essential to correctly diagnose and resolve B1673. Here are the key steps a technician or skilled DIYer should follow:

• Check for any other related DTCs (especially SRS/airbag or seat module codes).
• Visually inspect the wiring and connectors under the driver’s seat for damage, disconnection, or corrosion.
• Test the seat occupancy sensor with a digital multimeter for continuity and expected resistance values (refer to OEM specs).
• Ensure all connectors are fully seated and free from debris or moisture.
• If possible, use a scan tool to monitor live data from the seat occupancy input and check for plausible readings.
• Check related fuses and replace any that are blown.
• If all else checks out, consider testing or replacing the occupant detection module as per manufacturer guidance.

Possible Repairs for Code B1673 #

Depending on the root cause identified during diagnosis, several repair actions may resolve the issue. Always follow OEM procedures and safety precautions, especially when working near SRS components.

• Replace a faulty seat occupancy (weight) sensor.
• Repair or replace damaged wiring or connectors under the driver’s seat.
• Clean and secure corroded or loose connectors.
• Replace a defective occupant detection module.
• Replace blown fuses and investigate the cause of the short circuit.
• Remove or properly install aftermarket seat covers that could obstruct sensor function.

Is It Safe to Drive with Code B1673? #

Limited: While your vehicle may still function and drive normally, it is not recommended to drive for an extended period with code B1673 present. The reason is that occupant detection is a crucial input for airbag deployment logic. If the system cannot accurately detect the driver, the airbag may not deploy when needed, or it may deploy incorrectly. For your safety and that of your passengers, have the issue diagnosed and repaired as soon as possible.

Vehicles Most Commonly Affected by Code B1673 #

While B1673 can appear on any modern vehicle equipped with seat occupancy detection in the driver’s seat, it is reported more frequently on certain models and brands due to specific sensor designs or wiring configurations.

• Ford: Fusion, Focus, F-150, Explorer
• Lincoln: MKZ, Navigator
• Mercury: Milan, Mountaineer
• Toyota: Camry, RAV4, Corolla (with advanced airbag systems)
• GM: Chevrolet Malibu, Cadillac CTS, GMC Sierra
• Lexus: ES, RX series

Common Mistakes & Best Practices for Code B1673 #

Misdiagnosis or incomplete repairs can lead to recurring issues or even accidental airbag deployment. Here’s what to avoid and how to troubleshoot correctly:

• Neglecting to disconnect the battery before working around SRS components
• Overlooking simple wiring or connector faults under the seat
• Replacing the sensor without checking wiring harness integrity
• Using generic scan tools that can’t read all SRS or seat module data—OEM-level scanners are preferred
• Failing to recalibrate or reset the SRS control module after repairs if required by the OEM

Express FAQ for Code B1673 #

Below are quick answers to some common questions regarding B1673:

• Q: Can I just clear the code and ignore it?
  A: Clearing the code without fixing the root cause is not recommended. The issue will likely return, and occupant safety could be compromised.
• Q: Does this mean my airbags won’t work?
  A: The airbag system may not deploy correctly if the seat occupancy sensor isn’t functioning. Some systems may disable the airbag entirely for the driver seat, or default to a “safe” mode that isn’t optimal.
• Q: Do I need to replace the entire seat?
  A: Usually, only the sensor, wiring, or module needs replacement—not the entire seat. However, some OEMs integrate the sensor into the seat cushion, which may require more extensive work.