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Home / DTC / B1D55 — Passenger occupant detection sensor circuit fault

B1D55 — Passenger occupant detection sensor circuit fault

Detailed page for trouble code B1D55.

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B1D55

LAND ROVER B — Body

Passenger occupant detection sensor circuit fault

Brand: LAND ROVER
Type: B — Body
AI status
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Page language: EN

Causes

  • Damaged or disconnected seat occupancy sensor (seat mat)
  • Faulty occupant detection / classification module
  • Corroded, broken or shorted wiring harness/connectors under the passenger seat
  • Poor ground or lost reference voltage to the sensor/module
  • Intermittent connector contact from seat position/track movement
  • Software/firmware error or corrupted module calibration

Symptoms

  • SRS / Airbag warning lamp illuminated on instrument cluster
  • Passenger airbag disabled message or lamp (incorrect enable/disable)
  • Passenger occupied status incorrect in diagnostic live data (always empty/always occupied)
  • Seatbelt reminder or chime behavior inconsistent for passenger seat
  • Intermittent or persistent fault code stored; possible CAN communication warnings

What to check

  • Read all stored and pending SRS/occupant classification fault codes with a capable scan tool and record freeze frame/live data
  • Visually inspect passenger seat underside and seat cushion for damage, foreign objects, moisture or spillage
  • Inspect wiring harness and connectors under the seat for pin damage, corrosion, pulled wires, chafing at rails and connector retention
  • Check connector seating at occupant classification module and airbag/RCM (restraint control module)
  • With scan tool view live data for passenger occupancy status, sensor channel voltages/values and observe while moving the seat/pressing mat
  • Check for related communication codes (U0xxx) that would affect passenger detection

Signal parameters

  • Reference supply typically provided to sensor/module (commonly +5 V or vehicle 12 V supply — verify with service manual)
  • Signal output: sensor circuit may present a variable voltage or switched/digital status; expected idle/safe values defined in service literature
  • Open-circuit: infinite resistance / no signal; short-circuit: near 0 V or low resistance to ground — both indicate fault
  • Module communicates occupancy status over CAN or internal network; live-data status should toggle when pressure applied to seat mat

Diagnostic algorithm

  1. Follow manufacturer SRS safety procedure: disable battery/per service manual and wait required time before accessing airbag components
  2. Read and record all SRS/occupant classification codes; clear codes and re-check to confirm reproducibility.
  3. Perform visual inspection of the passenger seat cushion, seat mat, and underside for moisture, tears or damage. Remove seat trim as required.
  4. Inspect and gently tug harnesses and connectors under the seat; look for damaged wires at seat rails and under seat components.
  5. Reconnect and reseat all connectors; check for corrosion on terminals. Repair or replace damaged terminals as needed.
  6. With battery reconnected, using a diagnostic scan tool, monitor occupant detection live data and watch values while applying pressure to different areas of the seat mat and while moving seat fore/aft to find intermittent faults.
  7. Measure reference voltage and ground at the occupant sensor connector and at the occupant classification module against manufacturer specifications.
  8. Check sensor element resistance or capacitance per service manual. Replace seat mat/sensor if out of specification or open/shorted.
  9. If wiring and sensor are good, check module power/ground and CAN communication lines; if module not responding or shows internal errors, consider replacing occupant classification module or airbag control module per manufacturer procedures.
  10. After repairs, clear codes and verify correct occupancy reporting and that SRS warnings are extinguished. Perform any required calibration or module coding as specified.
  11. Note: Always follow Land Rover recommended procedures and safety precautions when working on SRS components.

Likely causes

  • Seat occupancy mat damaged or moisture ingress causing short or open circuit
  • Connector pin corrosion or loose terminal at seat harness or occupant classification module
  • Broken wire where harness flexes on seat frame (common at seat base/rails)
  • Faulty occupant classification module (internal electronics)

Fault status

⚠️ Status
Passenger occupant detection sensor circuit fault — electrical fault or implausible signal from passenger seat occupancy sensor. May disable passenger airbag or trigger SRS warning. Inspect sensor, wiring, connectors, and occupant classification module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0 - 3.0 hours

Similar codes

B1D54 B1D56 U0121 U0151 B0188
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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