Check The Mass Air Flow Sensor Unit

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

Fig 1: Connecting Battery Positive Terminal To Terminal No. 3
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Check the voltage changes when air is blown to the mass air flow sensor unit in arrow direction.

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