ENGINE (DIAGNOSTICS)(H4SO) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC DETECTING CONDITION:

Immediately at fault recognition

TROUBLE SYMPTOM:

• Erroneous idling

• Engine stalls.

• Poor driving performance

CAUTION:

After repairing or replacing the defective part, perform the Clear Memory Mode and Inspection Mode .

WIRING DIAGRAM:

STEP	CHECK	YES	NO
1.CONNECT SUBARU SELECT MONITOR AND READ DATA. 1) Turn the ignition switch to OFF. 2) Connect the Subaru Select Monitor to the data link connector. 3) Turn the ignition switch to ON and the Subaru Select Monitor power switch to ON. 4) Start the engine. 5) Read the voltage of mass air flow sensor using Subaru Select Monitor. NOTE: For detailed operation procedure, refer to “READ CURRENT DATA FOR ENGINE”.	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.
2.CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW SENSOR CONNECTOR. 1) Turn the ignition switch to OFF. 2) Disconnect the connector from mass airflow sensor. 3) Turn the ignition switch to ON. 4) Measure the voltage between mass air flow sensor connector and chassis ground. Connector & terminal (B3) No. 3 (+) — Chassis ground (−):	Is the voltage 5 V or more?	Repair the battery short circuit of harness between mass air flow sensor connector and ECM connector.
3.CHECK HARNESS BETWEEN ECM AND MASS AIR FLOW SENSOR CONNECTOR. 1) Turn the ignition switch to OFF. 2) Disconnect the connectors from the ECM. 3) Measure the resistance of harness between ECM connector and mass air flow sensor connector. Connector & terminal (B3) No. 2 — (B135) No. 34:	Is the resistance less than 1 Ω?	Replace the mass air flow sensor.	Repair the open circuit of harness between mass air flow sensor connector and ECM connector.