1.CHECK CURRENT DATA.
2) Read the data of engine coolant 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 engine coolant 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 engine coolant temperature sensor connectors.
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Is there poor contact in the ECM or engine coolant temperature sensor connectors?
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Repair any poor contact between the ECM and engine coolant temperature sensor connectors.
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3.CHECK HARNESS BETWEEN ECM AND ENGINE COOLANT TEMPERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM and engine coolant temperature sensor.
3) Measure the resistance of the harness between the ECM and engine coolant temperature sensor connector.
Connector & terminal
(B137) No. 11 — (E8) No. 2:
(B134) No. 29 — (E8) No. 1:
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Is the resistance less than 1 Ω?
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Repair the harness and connector.
NOTE:
In this case, repair the following item:
• Open circuit in harness between ECM and engine coolant temperature sensor connector
• Poor contact of coupling connector
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4.CHECK HARNESS BETWEEN ECM AND ENGINE COOLANT TEMPERATURE SENSOR CONNECTOR.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and chassis ground.
Connector & terminal
(B137) No. 11 (+) — 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 engine coolant temperature sensor connector.
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Replace the engine coolant temperature sensor.
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