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Home / DTC / B1A50 — Occupant Detection Sensor Circuit Fault

B1A50 — Occupant Detection Sensor Circuit Fault

Detailed page for trouble code B1A50.

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B1A50

LAND ROVER B — Body

Occupant Detection Sensor Circuit Fault

Brand: LAND ROVER
Type: B — Body
Views: UK: 17 EN: 36 RU: 20
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Page language: EN

Causes

  • Open or short circuit in occupant detection sensor wiring
  • Corroded, bent or disconnected seat connector pins
  • Faulty occupant detection mat/sensor module under the seat
  • Water/moisture ingress into the seat or connector
  • Poor repair or wiring damage after seat removal
  • Faulty SRS/airbag control module or software fault

Symptoms

  • SRS/Airbag warning light ON or intermittent
  • Passenger airbag status message may show ‘OFF’ or ‘Unavailable’
  • Passenger airbag enable/disable lamp behaves incorrectly
  • Possible seat belt reminder or occupant classification messages
  • Diagnostic trouble code stored and possibly related B1Axx codes present

What to check

  • Read stored DTCs and freeze frame data with an appropriate diagnostic tool
  • Check for related codes in SRS and body modules (communication/bus errors)
  • Visually inspect seat area for signs of water, damage, or foreign objects
  • Inspect connectors and wiring under the passenger seat for corrosion, loose pins, or chafing
  • Check SRS lamp operation and any instrument cluster messages
  • Review vehicle service history for recent seat removal or repairs and available technical service bulletins (TSBs)

Signal parameters

  • Occupant sensor reference supply typically 5 V (vehicle-specific) — verify exact factory value
  • Signal voltage range varies with load; expect a measurable change when applying weight (typical ~0.5–4.5 V depending on design)
  • Continuity/ohms of seat mat sensor circuit will change when simulating occupant load — compare to service data
  • Module communication via CAN/LIN (if used) should be present; check for bus errors
  • Look for short to battery or ground at connector pins (near 0 Ω to ground or battery)

Diagnostic algorithm

  1. Safety first: follow manufacturer SRS procedures — disable battery and wait the specified time before working on seat/airbag components
  2. Retrieve and record all codes and freeze frame, then clear codes to check reappearance
  3. Perform visual inspection under passenger seat: connectors, wiring routing, chafing points, moisture or foreign object evidence
  4. With battery reconnected and SRS powered, backprobe occupant sensor connector and verify reference voltage and signal while seat is unoccupied and while applying known weight (use manufacturer recommended method/weight)
  5. Perform wiggle test of harness and connectors while monitoring live signal to identify intermittent faults
  6. Measure continuity and resistance of sensor wiring from the occupant sensor connector to the airbag/occupant module; compare to factory specifications
  7. If open/short found, repair harness/connector and protect routing; replace damaged harness sections or pins as required
  8. If wiring and connector are good but sensor signal is implausible, replace the occupant detection mat/module per service procedures
  9. If fault persists after sensor/module replacement, inspect/replace occupant classification control module or perform SRS control module diagnostics and software updates as directed by manufacturer
  10. After repairs, clear codes, perform SRS self-test and confirm no codes return; verify passenger airbag status and instrument warnings

Likely causes

  • Damaged harness rub point under seat causing intermittent short to ground
  • Connector terminal corrosion due to spilled liquid or moisture ingress
  • Broken traces or welded joints inside the seat occupancy mat sensor
  • Connector not fully seated after seat removal or service
  • Failed occupant classification module (seat ECU) or internal electronics fault

Fault status

⚠️ Status
Occupant Detection Sensor Circuit Fault — open/short/implausible signal or communication error detected. Passenger airbag enablement may be affected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

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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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