If simulation function of M-MDS is not used:

Inspect variable swirl solenoid valve.
- If the variable swirl solenoid valve is not normal, replace the variable swirl solenoid valve.
- If the variable swirl solenoid valve is normal, inspect the following:
  - Vacuum hose and vacuum chamber for looseness or damage
  - Shutter valve actuator
  - Check valve is stuck open or closed
  - Shutter valve cannot move smoothly