B1673 — Seat Driver Occupied Input Circuit Open

What does OBD2 code B1673 mean?

OBD2 code B1673 flags a problem with the body electrical system (seat driver occupied input circuit open). The car is usually drivable while you plan the repair. Common culprits: body control module (BCM) fault, faulty switch, motor or actuator of the affected system, damaged wiring in door jambs or wet areas.

What are the symptoms of B1673?

Drivers most often notice: warning light on the dashboard, no impact on engine operation in most cases, the affected function (locks, windows, lighting, wipers) works intermittently or not at all.

How do I diagnose B1673 myself?

Start with a scan: confirm B1673, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the seat driver occupied input, and verify the suspect component against live data before buying parts.

How much does it cost to fix B1673?

Repair wiring or connectors — $80–$250; Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will B1673 clear itself?

Sometimes B1673 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

When your scanner pulls code B1673, it's telling you something specific: the vehicle's body control module has detected that the electrical path feeding the driver's seat occupancy signal has become interrupted. This falls squarely within the body electronics category of OBD2 codes, which handle comfort and convenience features rather than engine management. The term "circuit open" is the key descriptor here — it means current cannot complete its journey through that particular loop, so the module sees either zero volts or an infinite resistance reading where it expects to see a signal.

Modern vehicles use seat occupancy sensors for several functions: disabling the passenger airbag when a child seat is detected, adjusting air bag deployment force, or triggering related systems like seat belt reminders. When the circuit feeding this input opens up, the module loses communication with the sensor and logs B1673. It's worth noting that most control modules require the fault condition to appear repeatedly under specific operating parameters before illuminating the check engine light — a single brief glitch typically won't trigger this code. The freeze frame data stored alongside B1673 is extremely useful: it records engine load, RPM, coolant temperature, and vehicle speed at the moment the fault occurred, giving you a starting point for your diagnosis.

The actual culprit behind an open circuit condition usually comes down to one of a few common problems. Physical damage to wiring ranks highest — particularly in areas that flex repeatedly, like door jambs where wires pass through hinges. Connectors can back out slightly, allowing moisture and corrosion to creep in over time. A blown fuse feeding that particular circuit will obviously stop current flow entirely. Less frequently, the seat occupancy sensor itself or the body control module develops an internal failure. The good news is that body system faults rarely cause drivability problems — your engine will keep running, though some comfort features may misbehave.

Common Symptoms of B1673

• The check engine or body system warning light illuminates on the dashboard
• Engine performance and drivability remain unaffected in most vehicles
• The specific function tied to the seat occupancy input operates intermittently or stops working entirely
• Related systems like automatic locking, window controls, or interior lighting may behave erratically
• The airbag readiness light may accompany B1673 on some makes, since seat sensors feed into supplemental restraint logic
• Central locking can fail in rare cases, potentially leaving the vehicle unsecured

What Causes B1673?

• A break or chafing damage in the wiring harness near the driver's seat or door jamb
• A connector that has become unplugged, has a backed-out pin, or shows corrosion buildup
• A blown fuse dedicated to the seat occupancy or body control circuit
• Internal failure of the seat driver occupied input sensor or switch
• Poor electrical connections at the body control module or its input/output ports
• Wiring insulation degraded by heat, moisture, or chemical exposure in the passenger compartment
• Faulty body control module unable to process the input signal correctly

How to Diagnose B1673

Before replacing any parts, confirm the code exists and gather information:

1. Connect an OBD2 scanner and verify that B1673 is present and stored. Record the freeze frame data — this snapshot of engine conditions at the time of failure guides your testing later.
2. Pull all related codes from the body control module. Codes in the B0xxx range often share common causes, and addressing one may clear the others. Check manufacturer TSBs for your specific make and model — many body electrical issues have documented factory fixes or software updates.
3. Perform a visual inspection of the wiring and connectors associated with the driver's seat area. Look for torn insulation, exposed copper, white or green corrosion deposits, and any signs of prior repair work that may have been done incorrectly.
4. Run a continuity test on the seat occupancy input circuit from end to end. Gently wiggle the harness during testing — intermittent opens will show up as readings that jump around.
5. Monitor the relevant switch and motor parameters in live data while operating the affected system. Compare readings against known-good values from the same vehicle or service information.
6. Pay special attention to flex points — the door jambs, seat tracks, and hinge areas where wires bend every cycle. This is where fatigue breaks typically occur first.
7. Clear the code after your inspection and testing, then drive the vehicle through a complete drive cycle that reproduces the freeze frame conditions. If B1673 returns, the fault is confirmed and active.

Repair Options and Costs

Start troubleshooting with the least expensive possibilities before considering component replacement:

• Wiring repair or connector replacement: $80–$250
• Seat occupancy switch or actuator replacement: $120–$450
• Body control module repair or replacement: $300–$900

The total cost to resolve B1673 depends entirely on which part has failed. In most cases, the problem turns out to be a damaged wire or corroded connector — both relatively inexpensive to fix. BCM replacement represents the most costly scenario and should only be pursued after confirming the module itself is at fault, not just its inputs.

Can You Drive with B1673?

In the vast majority of situations, yes — B1673 does not impair engine operation or transmission function. The vehicle remains safe and legal to drive. The main exceptions involve safety-critical systems: if the fault affects exterior lighting, windshield wipers, or central locking, address those promptly. A car that cannot be secured properly presents a security concern, and impaired visibility in bad weather creates a safety hazard. Otherwise, you can continue driving and schedule repair at your convenience.

Related OBD2 Codes

• B1600: PATS Ignition Key Transponder Signal Is Not Received
• B1601: PATS Received Incorrect Key-Code From Ignition Key Transponder
• B1602: PATS Received Invalid Format Of Key-Code From Ignition Key Transponder
• B1603: Lamp Anti-Theft Indicator Circuit Failure
• B1604: Lamp Anti-Theft Indicator Circuit Open
• B1605: Lamp Anti-Theft Indicator Circuit Short To Battery

The B1673 OBD2 fault code relates to the Climate Control Air Temperature Internal Sensor Motor circuit. When the circuit circuit failure, the module cannot properly monitor or control this body system.

At AIscanAuto, we help drivers quickly identify OBD2 trouble codes, understand their root causes, and find the right fix.

Symptoms

• Climate control not responding
• A/C pressure issues
• Temperature not adjusting
• Possible blower motor issues

Common Causes

• Faulty component — internal damage or wear affecting Climate Control Air Temperature Internal Sensor Motor
• Wiring issues — broken, corroded, or chafed wires in the circuit
• Connector problems — loose, oxidized, or moisture-damaged pins
• a general circuit failure is detected — can result from wiring faults, connector issues, or component failure
• Module input failure — rare, but the control module input stage may be defective

Step-by-Step Diagnosis

1. Scan with OBD2 tool — Confirm B1673 is active. Check for additional DTCs.
2. Visual inspection — Examine the Climate Control Air Temperature Internal Sensor Motor wiring and connector for corrosion or damage.
3. Check voltage and ground — Use a multimeter to verify proper reference voltage.
4. Test component — Compare readings to factory specs. A stuck or erratic signal confirms failure.
5. Check for shorts/opens — Perform continuity tests on the wiring between the component and control module.

Repair & Solutions

• If the component is defective, replace the Climate Control Air Temperature Internal Sensor Motor with an OEM or quality aftermarket part.
• Repair any damaged wiring or connectors using proper methods.
• Clear the DTC with an OBD2 scanner and test drive to verify the code does not return.
• If the code persists after component replacement, inspect the control module connector.

Related Codes

• B1670 — Climate Control Air Temperature Internal Sensor Motor Circuit Failure
• B1671 — Climate Control Air Temperature Internal Sensor Motor Circuit Open
• B1672 — Climate Control Air Temperature Internal Sensor Motor Circuit Short To Battery