B1516

Seat Driver Occupied Switch Circuit Open

Body Chassis/Safety Occupant Detection 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The car's seat occupancy sensor for the driver's seat has a broken wire or loose connection, so the system can't tell if someone is sitting there. It's like a light switch that's disconnected—the circuit is open and won't send a signal.

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Symptoms You May Notice

3 known symptoms for this code
Airbag warning light illuminated on dashboard
Seat belt pretensioner may not function properly
Occupant detection system malfunction indicator
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the voltage signal from the driver seat occupancy switch, which should toggle between high and low states depending on seat pressure. An open circuit means the signal wire is broken or disconnected, preventing any voltage from reaching the ECU. The system interprets this as a fault condition rather than an empty seat.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Seat Occupancy Signal Voltage 0.5V to 4.5V (switching between states) No signal or open circuit (5.0V+)
Circuit Continuity Complete circuit path with <10Ω resistance Infinite resistance or open circuit detected
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Seat occupancy switch connector
Locate the connector under the driver seat and reseat it firmly to restore electrical contact.
2
Wiring harness for seat switch
Inspect the wire bundle from the seat to the module for damage or pinching and repair any visible breaks with electrical tape or replace the section.
3
Driver seat occupancy switch assembly
Remove the old switch from underneath the seat cushion and install a new OEM replacement if connector and wiring are intact.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1516 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code B1516

What happens after you fix the fault

Once the fault is repaired, B1516 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.