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Home / DTC / B1149 — Occupant Detection Sensor Circuit Malfunction

B1149 — Occupant Detection Sensor Circuit Malfunction

Detailed page for trouble code B1149.

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Code

B1149

Generic B — Body

Occupant Detection Sensor Circuit Malfunction

Brand: Generic
Type: B — Body
Views: UK: 1 EN: 1 RU: 3
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Page language: EN

Causes

  • Open or short in sensor wiring (power, ground, or signal)
  • Corroded, loose or damaged connector at seat/ECU
  • Failed occupant detection sensor (mat, pressure sensor, or sensor pad)
  • Water/moisture intrusion in seat cushion
  • Faulty restraint/airbag control module or module software error
  • Aftermarket seat covers, heaters, or repairs that alter sensor function

Symptoms

  • Airbag/RSI warning lamp illuminated or flashing
  • Passenger airbag enable/disable light behaves incorrectly (stays off or on when it shouldn’t)
  • Possible diagnostic trouble codes stored for occupant sensing system
  • In some vehicles, seatbelt reminder or other SRS messages may appear

What to check

  • Read and record stored codes, freeze frame and live data with a capable scan tool
  • Visually inspect passenger seat area for moisture, damage, or aftermarket items
  • Inspect connectors and wiring under the seat for corrosion, pin damage, or breaks
  • Wiggle seat and harness while watching live data to reproduce intermittent faults
  • Check for applicable technical service bulletins (TSBs) or recalls
  • Do not deploy airbags or attempt repairs that could cause inadvertent deployment; follow OEM SRS safety procedures

Signal parameters

  • Reference supply: typically 5 V or vehicle battery depending on design — verify with OEM data
  • Signal output: varies by design (voltage signal or resistance change) — should change when weight applied/removed
  • Expected open-circuit: infinite/OL between sensor signal and return when disconnected
  • Expected short: near 0 ohms between signal and ground or power indicates short
  • CAN/reservation flag: Occupant detection status bit(s) in SRS module message (present/absent)

Diagnostic algorithm

  1. Connect a factory-level scan tool. Read and document B1149 and any related SRS codes and freeze-frame data.
  2. Verify current occupant detection data using live data (occupant present flag, sensor voltage/resistance if available). Note behavior with/without a person on the seat.
  3. Perform a thorough visual inspection: remove seat trim as required and inspect connectors, terminal corrosion, wiring chafing and routing where it passes seat rails.
  4. With ignition on and SRS system in a safe state per OEM procedures, backprobe sensor connector and measure reference voltage, signal voltage, and ground continuity. Compare to OEM specs.
  5. Check continuity and resistance of sensor wiring to the SRS module; look for shorts to chassis ground or battery voltage.
  6. Perform a wiggle test on wiring and connectors while watching for changes in live data or DTCs to find intermittent faults.
  7. If wiring and connectors are good, disconnect sensor and measure sensor resistance or output directly according to OEM test (apply weight and observe expected change).
  8. If sensor fails bench/seat tests, replace occupant detection sensor/mat assembly per manufacturer procedures. Reinstall and retest.
  9. If new sensor still reports fault and wiring checks good, consider SRS control module fault — verify module power/ground and communication; consult OEM procedures before module replacement.
  10. After repairs, clear codes and perform a functional test (verify correct passenger airbag enable/disable behavior and that no SRS warning lamp remains).

Likely causes

  • Damaged or disconnected connector under passenger seat
  • Broken or shorted wiring between sensor and SRS module due to seat movement
  • Failed occupant detection mat or sensor assembly
  • Corrosion from spilled liquids in seat cushion

Fault status

⚠️ Status
Occupant detection sensor circuit malfunction detected. Check sensor, connectors, and wiring. May disable or misreport passenger airbag status.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1148 B1150 B1140 B1141 B1151
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