DTC P0102 Mass Or Volume Air Flow Circuit Low Input

WARNING: This page is about a different variant/trim than selected.

DTC DETECTING CONDITION:

Detect as soon as the malfunction occurs.
GENERAL DESCRIPTION < Ref. to DTC P0102 MASS OR VOLUME AIR FLOW CIRCUIT LOW INPUT , Diagnostic Trouble Code (DTC) Detecting Criteria. >

TROUBLE SYMPTOM:

Erroneous idling
Engine stalls.
Poor driving performance

CAUTION: After repair or replacement of faulty parts, conduct Clear Memory Mode < Ref. to , OPERATION , Clear Memory Mode.> and Inspection Mode < Ref. to , PROCEDURE , Inspection Mode.>.

WIRING DIAGRAM:

Fig 1: Wiring Diagram - DTC P0102 Mass Or Volume Air Flow Circuit Low Input

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE (DTC P0102)

Step	Check	Yes	No
1 READ THE DATA CONNECTING SUBARU SELECT MONITOR OR OBD-II GENERAL SCAN TOOL. Turn the ignition switch to OFF. Connect the Subaru Select Monitor to data link connector. Turn the ignition switch to ON, and the Subaru Select Monitor switch to ON. Start and idle the engine. Read the voltage of mass air flow sensor using Subaru Select Monitor or OBD-II general scan tool. NOTE: Subaru Select Monitor For detailed operation procedure, refer to the "READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE". < Ref. to , SUBARU SELECT MONITOR . > OBD-II general scan tool For detailed operation procedure, refer to the OBD-II general scan tool instruction manual .	Is the voltage 0.2 - 4.7 V?	Even if the malfunction indicator light illuminates, the circuit has returned to a normal condition at this time. A temporary poor contact of the connector or harness may be the cause. Repair harness or connector in the mass air flow sensor. NOTE: In this case, repair the following: Open or ground short circuit in harness between mass air flow sensor and ECM connector Poor contact in mass air flow sensor or ECM connector	Go to step 2.
2 CHECK INPUT SIGNAL FROM ECM. Measure the voltage between ECM connector and chassis ground while engine is idling. Connector & terminal (B136) No. 23 (+) - Chassis ground (-):	Is the voltage more than 0.2 V?	Go to step 4.	Go to step 3.
3 CHECK INPUT SIGNAL FOR ECM (USING SUBARU SELECT MONITOR). Measure the voltage between ECM connector and chassis ground while engine is idling.	Does the voltage change by shaking the harness and connector of ECM while monitoring the value with Subaru Select Monitor?	Repair the poor contact in ECM connector.	Replace and check it again because of ECM malfunction possibility.
4 CHECK POWER SUPPLY TO MASS AIR FLOW SENSOR. Turn the ignition switch to OFF. Disconnect the connector from mass air flow sensor. Turn the ignition switch to ON. Measure voltage between mass air flow sensor connector and chassis ground. Connector & terminal (B3) No. 1 (+) - Chassis ground (-):	Is the voltage more than 10 V?	Go to step 5.	Repair the open circuit between mass air flow sensor and main relay.
5 CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW SENSOR CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector from ECM. Measure the resistance of harness between ECM and mass air flow sensor connector. Connector & terminal (B136) No. 23 - (B3) No. 3: (B136) No. 31 - (B3) No. 2: B136 No. 35 - (B3) No. 5:	Is the resistance less than 1 ?	Go to step 6.	Repair the open circuit between ECM and mass air flow sensor connector.
6 CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW SENSOR CONNECTOR. Measure the resistance of harness between ECM and chassis ground. Connector & terminal (B136) No. 23 - Chassis ground: (B136) No. 31 - Chassis ground: (B136) No. 35 - Chassis ground:	Is the resistance more than 1 M?	Go to step 7.	Repair the ground short circuit between ECM and mass airflow sensor connector.
7 CHECK POOR CONTACT. Check poor contact in mass air flow sensor connector.	Is there poor contact in mass air flow sensor connector?	Repair the poor contact in mass air flow sensor connector.	Replace the mass air flow and intake air temperature sensor. < Ref. to MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR . >