LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Subaru >> 1995 >> Legacy Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Code Testing >> DTC P0100 (QA) - Mass Air Flow (MAF) Sensor Circuit Malfunction
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0100 (QA) - Mass Air Flow (MAF) Sensor Circuit Malfunction

NOTE: Refer to illustration for connector and terminal identification. See Figure -Figure .
  1. Turn ignition to OFF. After Connecting SSM or OBD-II scan tool, turn ignition to ON. Turn SSM or OBD-II scan tool to ON. Start Engine. Set function mode on SSM to F08 to read voltage input from MAF sensor or F47 to read mass air flow in g/sec. If sensor input voltage is 0.3-5.0 volts and/or mass air flow is 1.3-250 g/sec, check for a poor connection, short or open in sensor circuit or ground wires and repair as necessary. If value reading is less than 0.3 volt (1.3 g/sec), go to step 2). If wiring is good and reading is not less than 0.3 volt (1.3 g/sec), go to step 5).
  2. Measure voltage between ECM connector B84, terminal No. 26 and ground. If voltage is 0.3 volt or less, go to next step. If voltage is more than 0.3 volt while shaking harness and connector, repair contact in ECM connector. If voltage remains below 0.3 volt, replace ECM.
  3. Turn ignition to OFF. Disconnect connector from MAF. Turn ignition to ON. Measure voltage between MAF connector B3, terminal No. 1 and ground. If voltage is 10 volts or more, go to next step. If voltage is less than 10 volts, repair open circuit in harness between main relay connector and MAF connector.
  4. Turn ignition to OFF. Disconnect ECM connector. Measure resistance of harness connector between ECM connector B84, terminal No. 26 and MAF connector B3, terminal No. 4, between ECM connector B84, terminal 46 and MAF connector B3, terminal No. 3, and between ECM connector B84, terminal No. 25 and MAF connector B3, terminal No. 2. If resistance is 10 ohms or less in each or any instance, replace MAF sensor. If resistance is greater than 10 ohms, repair poor contact or open circuit in harness between ECM and MAF sensor connector.
  5. Turn ignition to OFF. Disconnect MAF sensor connector. With SSM connected, turn ignition to ON. Turn SSM ON and select function mode F08. If voltage reads more than 5 volts, repair short circuit in harness between ECM and MAF. If voltage is less than 5 volts, check for poor contact in MAF sensor connector. If contact is bad, repair as necessary. If contact is okay, replace MAF sensor.
scientia non olet · About LEMON Manuals