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Home / DTC / B1D1A — Occupant Detection Sensor Circuit Fault — Front Passenger Seat

B1D1A — Occupant Detection Sensor Circuit Fault — Front Passenger Seat

Detailed page for trouble code B1D1A.

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B1D1A

LAND ROVER B — Body

Occupant Detection Sensor Circuit Fault — Front Passenger Seat

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

Causes

  • Open or short in occupant detection sensor wiring
  • Poor or corroded connector contact under the passenger seat
  • Failed occupant detection mat or seat occupant module
  • Water ingress or contamination of the seat wiring/connectors
  • Faulty SRS/airbag control module or software/configuration mismatch
  • Intermittent fault caused by seat movement (chafed wiring or pinched harness)

Symptoms

  • SRS/airbag warning lamp illuminated
  • Passenger airbag status lamp shows disabled or inconsistent indication
  • Passenger airbag may not enable even when seat is occupied
  • DTC B1D1A stored in SRS/airbag module
  • Possible intermittent airbag system faults or warnings

What to check

  • Read and record stored SRS codes and freeze frame data with an OEM-capable scan tool
  • Visually inspect underside of front passenger seat for damaged wiring, connectors, debris or moisture
  • Check connector retention and pin condition at the occupant sensor/seat module
  • Monitor live data/occupancy status on the scan tool while applying weight to the seat
  • Perform a wiggle test on the seat harness while watching live data and DTCs
  • Confirm reference voltage and ground at the sensor connector with ignition ON

Signal parameters

  • Reference supply typically 5 V (±0.5 V) from seat/airbag module — verify with OEM data
  • Signal type: either analog voltage proportional to sensor resistance (approx. 0–5 V) or processed occupancy status via seat module/CAN — confirm with vehicle wiring diagrams
  • Open circuit: very high/infinite resistance; short to ground: near 0 Ω
  • Typical occupancy sensor resistance changes when weight applied (values vary by design; measure relative change rather than absolute without OEM spec)
  • CAN/LIN messages (if used) should show valid seat occupancy status flags; loss of frames indicates communication issue

Diagnostic algorithm

  1. Connect an OEM-capable SRS scan tool. Record DTCs, freeze frame and live data for the passenger occupant sensor.
  2. With battery voltage stable and ignition ON (follow manufacturer safety precautions for SRS work), visually inspect the passenger seat underside and seat rail area for damage, trapped objects, or moisture.
  3. Inspect and gently wiggle the occupant sensor connector(s). Unplug and inspect pin condition and corrosion. Reconnect firmly.
  4. With connector connected, measure reference voltage and ground at the sensor connector. Verify supply and ground are within specified tolerance (typically ~5 V reference).
  5. Measure sensor signal while applying known weight to the seat. Observe live data for expected change (or occupancy flag). If no change, measure resistance across sensor terminals (compare to factory values or check for open circuit).
  6. Perform continuity checks between sensor connector and SRS/seat module connector to find opens/shorts; inspect shielding and grommets where harness flexes.
  7. Perform a wiggle test and repeat steps 4–6 to try to reproduce the fault. Note if code is intermittent and conditions when it appears.
  8. If wiring and connectors are good, consider bench/seat module swap or replacement of the occupant detection mat per OEM procedure. Always follow SRS handling and replacement guidelines.
  9. After repair, clear codes, perform required system initialisation/calibration per manufacturer, and verify with functional tests and another road/seat test.

Likely causes

  • Damaged/chafed harness where it passes through seat frame (most common)
  • Loose or corroded multi‑pin connector at the occupant sensor or seat module
  • Failed occupant detection mat (resistive sensor elements shorted or open)
  • Detached/poor ground or missing 5V reference at the sensor connector
  • Aftermarket seat or prior repair left connectors mismatched or pins damaged
  • Fault in the restraint control (SRS) module or a software/configuration error

Fault status

⚠️ Status
Front passenger occupant detection sensor circuit fault detected. Possible open/short/intermittent connection or invalid sensor signal — passenger airbag enablement may be affected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-3 hours

Similar codes

B1D1B B1D0A B1D2A B183F B1D1C
320

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