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Home / DTC / B1B31 — Key of identifier 29

B1B31 — Key of identifier 29

Detailed page for trouble code B1B31.

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22,491specific
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Code

B1B31

LAND ROVER B — Body

Key of identifier 29

Brand: LAND ROVER
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Key transponder not programmed or deleted from vehicle database
  • Damaged or failed key transponder (physical damage, water ingress)
  • Weak or dead key battery (affects RF fob, sometimes programming/read functions)
  • Faulty key read antenna (LF coil) or damaged wiring/connectors
  • Intermittent or failed communication on vehicle network (CAN/LIN) between immobiliser, BCM and ECU
  • Software/configuration mismatch or corrupted data in immobiliser/BCM

Symptoms

  • Engine cranks but will not start or no crank/no start condition
  • Immobiliser or key warning lamp illuminated on instrument cluster
  • Key not being recognised message on dash or infotainment
  • Intermittent start/fail behaviour depending on which key is used
  • Remote keyless entry or remote start functions may be inoperative
  • Possible loss of other body functions if BCM/immobiliser has broader faults

What to check

  • Confirm exact fault code and freeze-frame data with a Land Rover approved diagnostic tool
  • Try a known-good spare key to see if problem follows the key or the vehicle
  • Check and, if needed, replace the key fob battery and retest
  • Inspect key for physical damage, water ingress or altered transponder head
  • Scan for related communications/network codes (U-codes) and check CAN bus health
  • Visually inspect antenna/immobiliser module wiring, connectors and grounds for damage/corrosion

Signal parameters

  • Transponder read result / key ID (expected: valid programmed ID entry for this vehicle)
  • LF antenna coil continuity/resistance (manufacturer-specific; typically low ohms)
  • Key fob battery voltage (expected ~3.0 V for most smart keys / 12 V for remote battery packs if applicable)
  • CAN bus idle voltage (~2.5–3.5 V) and message flow between immobiliser, BCM and engine ECU
  • Immobiliser authentication response codes / status flags returned by BCM
  • RF downlink/uplink frequency presence for remote key (vehicle-specific 315/433 MHz or country variant)

Diagnostic algorithm

  1. Read and record the full fault list and freeze-frame data with a dealer-level diagnostic tool.
  2. Attempt start with each available key to determine if issue is key-specific. If a spare works, suspect defective/unprogrammed primary key.
  3. Replace the key fob battery and retest key recognition.
  4. Use diagnostic tool to read stored key identifiers from the immobiliser/BCM. Verify if identifier 29 is present and correctly formatted.
  5. Inspect key and antenna wiring/connectors for damage or corrosion. Check antenna coil continuity and connector voltages.
  6. Monitor CAN bus while attempting to start to confirm communication between immobiliser/BCM and engine ECU. Address any U-codes first.
  7. If key is not programmed, perform key learning/programming procedure per manufacturer service manual using approved diagnostic equipment.
  8. If key ID is present but authentication fails, perform immobiliser/BCM software/version checks and consider reflash/update per service bulletin.
  9. If hardware fault suspected (antenna, BCM or immobiliser module), replace failed component and re-program keys as required.
  10. Clear codes, retest multiple start cycles and confirm all related functions operate normally. Document steps and retained keys.

Likely causes

  • Key not present in vehicle key list (not programmed)
  • Failed/weak key battery preventing RF transmission or proper read
  • Antenna/coils around the ignition or push-button unit failing to read transponder
  • Intermittent CAN comms preventing the immobiliser from validating the key
  • Immobiliser or BCM fault (hardware or corrupted memory) less likely but possible

Fault status

⚠️ Status
Key identifier 29 not recognised / immobiliser authentication failed
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

B1B30 B1B32 U0155 U0401 P0606
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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