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Home / DTC / B1A24 — Transponder ID not registered

B1A24 — Transponder ID not registered

Detailed page for trouble code B1A24.

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Code

B1A24

MITSUBISHI B — Body

Transponder ID not registered

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

Causes

  • New or replacement key/transponder has not been programmed to the vehicle
  • Key transponder damaged or defective
  • Antenna coil (around ignition or push‑button module) not reading transponder
  • Faulty immobilizer/BCM or body ECU
  • Wiring/connectors/ground fault between antenna coil and immobilizer ECU
  • Loss of immobilizer memory after battery removal, ECU replacement or power surge

Symptoms

  • Engine cranks but will not start (no fuel injection or ignition cut)
  • Security/immobilizer indicator illuminated or flashing on dash
  • Key/remote may be refused by vehicle (no recognition)
  • Intermittent no‑start when using a specific key
  • No CAN/immobilizer status or inconsistent key ID reported by diagnostic tool

What to check

  • Try starting with all known good keys; note if any key works
  • Scan vehicle with an OEM or qualified diagnostic tool for immobilizer and engine ECU codes
  • Observe immobilizer/security lamp behavior during key operation and crank
  • Use diagnostic tool to read the transponder/key ID reported by the immobilizer
  • Inspect antenna coil and connector at the ignition switch or push‑button module for damage, corrosion, or loose connection
  • Verify power and ground to immobilizer/BCM and antenna module

Signal parameters

  • Transponder frequency (typical passive RFID): ~125 kHz (varies by system)
  • Key ID: unique transponder identifier read by immobilizer (hex/string)
  • Immobilizer status messages on diagnostic bus: key detected / key not registered / immobilizer armed
  • CAN messages: immobilizer module to ECU allowing fuel/ignition enable (presence/absence)
  • Expected response: immobilizer grants engine enable when key ID matches stored ID

Diagnostic algorithm

  1. Confirm symptom: replicate no‑start and note immobilizer indicator behavior.
  2. Scan immobilizer/BCM and engine ECU; record all stored and pending codes and freeze frame data.
  3. Test with a known good/programmed key. If vehicle starts, suspect the original key/transponder.
  4. If no known good key, use diagnostic tool to read the transponder ID presented when key is inserted or when starting; compare to stored key list in immobilizer.
  5. Inspect antenna coil/reader at ignition/push button for physical damage, correct connector seating and continuity to immobilizer unit.
  6. Check immobilizer module power and ground rails with a multimeter; verify CAN/serial communication between immobilizer and engine ECU using scan tool.
  7. If antenna and wiring are OK but key not recognized, attempt to register the transponder/key using the OEM programming procedure and tool (follow vehicle‑specific procedure).
  8. After programming, clear codes and retest multiple keys. If programming fails, record any tool errors and consider immobilizer module replacement or reflash as required.
  9. If intermittent recognition remains, inspect for electromagnetic interference sources or replace suspect keys/antennas as a logical next step.
  10. If immobilizer module or BCM is suspected, follow manufacturer guidance for immobilizer module diagnostics and replacement; ensure correct module coding and key programming after replacement.

Likely causes

  • Unprogrammed/new key or key battery failure
  • Damaged/non‑functional transponder inside the key
  • Antenna coil or reader fault at the ignition or push‑start module
  • Immobilizer unit or module communication/power fault

Fault status

⚠️ Status
Transponder ID not registered — the immobilizer does not recognize the key transponder. Key must be programmed or immobilizer/antenna fault repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

Similar codes

B1A23 B1A25 B2799 U0100 U0422
406

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