Check The Mass Air Flow Sensor Unit

Remove the mass air flow and intake air temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR>REMOVAL .
NOTE: Do not disconnect the connector.
Turn the ignition switch to ON. (Engine OFF)
Using the Subaru Select Monitor, read the intake air amount.
2.0 L model:

Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DATA MONITOR .

2.5 L model:

Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.5)>DATA MONITOR .
Check that the intake air amount changes when air is blown to the mass air flow sensor unit in the arrow direction.
CAUTION: Be careful that no dust enter inside the unit when air is blown.

Courtesy of SUBARU OF AMERICA, INC.
After inspection, install the related parts in the reverse order of removal.