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 procedures, refer to “READ CURRENT DATA FOR ENGINE”. 
• General scan tool
For detailed operation procedures, refer to the general scan tool operation manual.
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Is the intake air temperature less than −40°C (−40°F) ?
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Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the fault condition, and reperform the check.
NOTE:
In this case, there may be a temporary connector contact failure.
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2.CHECK FOR POOR CONTACT.
Check for poor contact between the ECM and the mass air flow and intake air temperature sensor connectors.
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Is there poor contact in the ECM or the mass air flow and intake air temperature sensor connectors?
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Repair any poor contact between the ECM and the mass air flow and intake air temperature sensor connectors.
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3.CHECK HARNESS BETWEEN ECM, MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR CONNECTORS.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the ECM and the mass air flow and intake air temperature sensor.
3) Measure the resistance of harness between ECM and mass air flow and intake air temperature sensor connectors.
Connector & terminal
(B135) No. 18 — (B3) No. 1:
(B135) No. 30 — (B3) No. 2:
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Is the resistance less than 1 Ω?
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Repair the open circuit of harness between the ECM and mass air flow and intake air temperature sensor connectors.
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4.CHECK HARNESS BETWEEN ECM, MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR CONNECTORS.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and chassis ground.
Connector & terminal
(B135) No. 18 (+) — Chassis ground (−):
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Is the voltage 5 V or more?
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Repair the short circuit to power in the harness between the ECM and the mass air flow and intake air temperature sensor connectors.
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Replace the mass air flow and intake air temperature sensor.
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