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Home / DTC / B1D02 — Occupant Detection Module - Communication Fault

B1D02 — Occupant Detection Module - Communication Fault

Detailed page for trouble code B1D02.

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B1D02

LAND ROVER B — Body

Occupant Detection Module - Communication Fault

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

Causes

  • Faulty occupant detection module (internal electronics or firmware)
  • Open, short or high resistance in CAN/LIN communication wiring or connectors
  • Poor or missing module power supply or ground
  • Corroded/water-damaged connector at the ODM or harness
  • Network termination or bus fault (missing/incorrect resistor, short to battery/ground)
  • Conflicting device or software mismatch after module replacement or update

Symptoms

  • SRS / airbag warning lamp illuminated
  • Passenger airbag disabled or incorrect airbag enable/disable behavior
  • Driver information messages about passenger detection or seat occupancy
  • Failure to register passenger presence; incorrect seatbelt/airbag behavior
  • Stored communication-related DTCs (B1D02 and possibly U0xxx codes)
  • Intermittent or permanent loss of module in diagnostic tool network list

What to check

  • Read all stored DTCs and freeze frame with a capable OEM or equivalent scan tool; note associated U-codes
  • Verify the occupant detection module appears in the vehicle network list and attempt to communicate with it
  • Visually inspect ODM connector, pins and harness for corrosion, bent pins, water ingress or damage
  • Check fuses and relays that supply the ODM for continuity and correct voltage
  • Measure module supply voltage and ground at the connector with key on; verify good ground return
  • Measure CAN_H and CAN_L voltages at the module connector (idle and during bus activity)

Signal parameters

  • CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (recessive), dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (approx.)
  • Differential voltage during dominant bits: ~2.0 V (approx. acceptable range depends on OEM spec)
  • Bus termination: ~60 Ω measured between CAN_H and CAN_L (two 120 Ω terminations in parallel)
  • CAN bus baud: typical high-speed CAN ≈ 500 kbps (some networks may use 125/250 kbps or low-speed CAN segments) — confirm with OEM data
  • Module supply: nominal battery voltage (9–16 V) present at power pins with key on; ground resistance low (
  • Message presence: ODM should transmit defined occupant/detection frames — verify with OEM diagnostic data or oscilloscope

Diagnostic algorithm

  1. Use a compatible diagnostic tool to read all SRS and network trouble codes; record freeze frame and network status.
  2. Check for related U-codes (lost CAN communication). If multiple modules are not present, suspect bus or gateway.
  3. Visually inspect the ODM connector and harness for damage, corrosion or signs of water ingress; repair any physical damage.
  4. With ignition on, measure battery voltage at the module power pin and check ground. Repair blown fuses or poor grounds before continuing.
  5. With ignition on, check CAN_H/CAN_L voltages at the module connector. Compare to expected values; look for stuck high/low or open circuit.
  6. Power off and measure termination resistance across CAN_H and CAN_L. Replace missing/incorrect termination or correct wiring faults.
  7. Use an oscilloscope or bus analyzer to observe CAN traffic while operating system functions that should generate occupant messages. Confirm presence/quality of messages.
  8. If wiring and power/ground are good but no communication, attempt a diagnostic session to reflash or reconfigure the ODM if an update is available and recommended by OEM.
  9. If the module still does not communicate and wiring/power/termination are verified, replace the occupant detection module per OEM procedures and program/configure as required.
  10. After any repair, clear codes and perform full system self-tests and a road test or pedestal test to confirm proper operation. Re-scan for codes and verify no new communication faults.

Likely causes

  • Damaged or loose connector/pin at the occupant detection module
  • Open/short in CAN bus wiring between the ODM and gateway/airbag ECU
  • ODM has lost power or ground (blown fuse, poor ground)
  • ODM internal failure or corrupted firmware (less common than wiring)
  • Network termination missing or incorrect causing bus communication errors

Fault status

⚠️ Status
Occupant Detection Module communication fault detected. SRS/passenger airbag status may be unavailable or incorrect. Inspect module power/ground, connectors and vehicle communication bus.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

B1D00 B1D01 B1D03 U0073 U0100
320

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