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Home / DTC / B3902 — Passenger Seat Occupant Detection Sensor Circuit Open

B3902 — Passenger Seat Occupant Detection Sensor Circuit Open

Detailed page for trouble code B3902.

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Code

B3902

Generic B — Body

Passenger Seat Occupant Detection Sensor Circuit Open

Brand: Generic
Type: B — Body
Views: UK: 0 EN: 2 RU: 0
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Page language: EN

Causes

  • Broken or disconnected wiring (open circuit) to the passenger seat sensor
  • Poor or corroded connector at the seat sensor or control module
  • Damaged or failed seat occupant detection sensor (mat, weight sensor, or pressure sensor)
  • Water intrusion or contamination in the seat electrical connector
  • Aftermarket seat/heating modification or poor previous repair
  • Faulty airbag/occupant classification module (less common)

Symptoms

  • SRS / airbag warning lamp illuminated
  • Passenger airbag status light may show 'OFF' when occupied or not illuminate correctly
  • Passenger seat belt reminder may behave incorrectly
  • Occupant classification (weight detection) not functioning
  • Possible disablement of passenger airbag deployment

What to check

  • Retrieve freeze-frame data and additional SRS codes with a capable scan tool
  • Visual inspection of passenger seat underside: connectors, wiring, clips, and routing
  • Check for signs of water, corrosion, or damage in the seat connector and harness
  • Perform continuity check between seat sensor connector and occupant classification module
  • Measure sensor signal and reference voltages with ignition ON (follow safety procedures)
  • Wiggle test while monitoring live data for intermittent open/restore

Signal parameters

  • Reference supply: typically a low-voltage reference (commonly ~5 V) — verify with vehicle manual
  • Signal voltage: varies with sensor type (0–5 V expected in many systems); open circuit will show no signal or infinite resistance
  • Resistance/continuity: an open circuit reads OL/infinite between sensor and module pins; occupied sensor resistance will differ from unoccupied — refer to manufacturer specs
  • Communications: some systems report seat sensor status via CAN or module input; check live-data values for seat occupancy status

Diagnostic algorithm

  1. Read and record all SRS/occupant classification codes and live-data values; note freeze-frame if present.
  2. Disconnect battery per manufacturer safety procedure before accessing under-seat connectors (to avoid accidental airbag deployment).
  3. Visually inspect the passenger seat underside, connectors, and harness for disconnection, pin damage, corrosion, or moisture.
  4. Reconnect battery and with ignition ON, use a scan tool to monitor seat occupancy sensor data while performing a wiggle test on the harness and connectors.
  5. With ignition OFF, disconnect the sensor connector and check continuity between the sensor connector and the occupant classification module connector pins; repair any open circuits.
  6. Measure reference and signal voltages at the sensor connector with ignition ON (safe distance from airbag components) and compare to expected values per manufacturer.
  7. If open is at the sensor, test or replace the seat occupant sensor assembly (mat/load cell) if required; repair damaged wiring or connectors as needed.
  8. After repairs, clear codes, perform any required occupant classification / SRS calibrations per manufacturer, and verify correct operation and that the SRS lamp is extinguished.
  9. If wiring and sensor check good but fault persists, consider module fault and refer to manufacturer procedures for module testing/replacement.

Likely causes

  • Disconnected or pinched connector under the passenger seat
  • Wiring harness damaged by seat movement or recliner mechanism
  • Corroded connector due to spilled liquids
  • Failed sensor element in the seat cushion

Fault status

⚠️ Status
Passenger seat occupant detection sensor circuit open — open/interrupt detected in the passenger seat occupancy sensor circuit. May disable passenger airbag or cause SRS warning lamp.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B3900 B3901 B3903 B3910 B3911
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