Check Mass Air Flow Sensor Unit

Connect battery positive terminal to terminal No. 3 and battery ground terminal to terminal No. 4, circuit tester positive terminal to terminal No. 5 and the circuit tester negative terminal to terminal No. 4.

Fig 1: Checking Mass Air Flow Sensor Unit
Courtesy of SUBARU OF AMERICA, INC.
Check that the voltage changes when air is blown to the mass air flow sensor unit from arrow direction.

Fig 2: Blowing Air Direction On Mass Air Flow Sensor Unit
Courtesy of SUBARU OF AMERICA, INC.