P1606 – Idle Air Control / Rough Idle (Toyota)

Description

The ECM detected improper idle air control operation affecting airflow and idle stability.

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Symptoms

  • Rough idle
  • Low idle speed
  • Engine shaking
  • Possible stalling
  • Poor throttle response

Causes

  • Faulty idle air control valve
  • Vacuum leaks
  • Dirty throttle body
  • Weak ignition components
  • ECM idle adaptation lost

Diagnosis

  • Inspect IAC valve
  • Check vacuum hoses
  • Clean throttle body
  • Test ignition coils
  • Perform idle relearn

Repair

  • Replace IAC valve
  • Repair vacuum leaks
  • Clean throttle body
  • Replace coils if needed

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