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