B1673
Seat Driver Occupied Input Circuit Open
Body Chassis/Safety Airbag/Occupancy Detection 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

The car's seat occupancy sensor isn't sending a signal to the computer, like a light switch with a broken wire. The ECU can't detect whether someone is sitting in the driver's seat.

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Symptoms You May Notice
3 known symptoms for this code
Airbag warning light illuminated on dashboard
Seat belt warning may malfunction or not activate
Airbag system may be disabled or non-functional
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the driver seat occupancy switch for a valid signal voltage when the ignition is on. This sensor tells the airbag control module whether to arm the airbag system. An open circuit means the expected voltage signal is never detected.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Seat Occupancy Signal Voltage 4.5-5.5V (closed switch) or 0V (open switch with valid transition) No voltage transition or stuck signal for >2 seconds
Circuit Resistance < 10 ohms (closed) or > 1M ohm (open) Open circuit (infinite resistance) detected
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Seat occupancy switch connector
Inspect and reseat the connector under the driver seat to restore electrical contact.
2
Wiring harness and connectors
Check for corroded or damaged wires between the seat switch and the airbag control module; clean or replace as needed.
3
Seat occupancy switch assembly
Replace the switch if it's internally broken or the contact is permanently open.