1.CHECK CURRENT DATA.
2) Read the data of intake air temperature sensor signal using Subaru Select Monitor or general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to “READ CURRENT DATA FOR ENGINE”. 
• General scan tool
For detailed operation procedure, refer to the general scan tool operation manual.
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Is the temperature less than −36°C (−33°F)?
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Repair the poor contact.
NOTE:
In this case, repair the following item:
• Poor contact in mass air flow and intake air temperature sensor
• Poor contact in ECM
• Poor contact of joint connector
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2.CHECK HARNESS BETWEEN MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the mass air flow and intake air temperature sensor.
3) Measure the voltage between mass air flow and intake air temperature sensor connector and engine ground.
Connector & terminal
(B3) No. 4 (+) — Engine ground (−):
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Is the voltage 10 V or more?
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Repair the short to power supply in harness between the mass air flow and intake air temperature sensor and ECM connector.
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3.CHECK HARNESS BETWEEN MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between mass air flow and intake air temperature sensor connector and engine ground.
Connector & terminal
(B3) No. 4 (+) — Engine ground (−):
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Is the voltage 10 V or more?
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Repair the short to power supply in harness between the mass air flow and intake air temperature sensor and ECM connector.
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4.CHECK HARNESS BETWEEN MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR AND ECM CONNECTOR.
Measure the voltage between the mass air flow and intake air temperature sensor, manifold absolute pressure sensor connector, and engine ground.
Connector & terminal
(B3) No. 4 (+) — Engine ground (−):
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Is the voltage 4 V or more?
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Repair the harness and connector.
NOTE:
In this case, repair the following item:
• Open circuit in harness between mass air flow and intake air temperature sensor and ECM connector
• Poor contact in mass air flow and intake air temperature sensor
• Poor contact in ECM
• Poor contact of joint connector
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5.CHECK HARNESS BETWEEN MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between mass air flow and intake air temperature sensor and engine ground.
Connector & terminal
(B3) No. 5 — Engine ground:
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Is the resistance less than 5 Ω?
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Replace the mass air flow and intake air temperature sensor. 
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Repair the harness and connector.
NOTE:
In this case, repair the following item:
• Open circuit in harness between mass air flow and intake air temperature sensor and ECM connector
• Poor contact in mass air flow and intake air temperature sensor
• Poor contact in ECM
• Poor contact of joint connector
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