P1616 – Immobilizer ECM Error (Toyota)

Description

The ECM detected an internal immobilizer-related malfunction affecting engine authorization.

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Symptoms

  • No start condition
  • Security light on
  • Intermittent start
  • Key not recognized
  • Failsafe mode

Causes

  • Internal ECM fault
  • Memory corruption
  • Voltage instability
  • Connector corrosion
  • Wiring issues

Diagnosis

  • Scan ECM
  • Inspect connectors
  • Check voltage stability
  • Test immobilizer communication
  • Verify grounds

Repair

  • Repair wiring
  • Clean connectors
  • Stabilize voltage
  • Replace ECM if necessary

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