P1521 – Intake Manifold Runner Stuck Open (Nissan)

Description

The ECM detected the intake manifold runner stuck in the open position.

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Symptoms

  • Low torque
  • Hesitation

Causes

  • Carbon buildup
  • Actuator failure
  • Vacuum leak

Diagnosis

  • Inspect runner movement
  • Check vacuum lines
  • Scan IMRC data

Repair

  • Clean runners
  • Replace actuator