P1618 – Immobilizer Transponder Error (Toyota)

Description

The ECM detected a malfunction in the key transponder signal, preventing proper immobilizer authentication.

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Symptoms

  • No start condition
  • Key not recognized
  • Security light flashing
  • Intermittent start
  • Immobilizer warning

Causes

  • Weak transponder
  • Damaged key
  • Signal interference
  • Faulty antenna coil
  • Immobilizer ECU fault

Diagnosis

  • Test key transponder
  • Inspect antenna coil
  • Check wiring
  • Scan immobilizer system
  • Verify ECM communication

Repair

  • Replace key
  • Replace antenna coil
  • Repair wiring
  • Replace immobilizer ECU

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