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.
|
Is the engine coolant temperature −40°C (−40°F) ?
|
|
Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.
NOTE:
In this case, temporary poor contact of connector may be the cause.
|
2.CHECK POOR CONTACT.
Check for poor contact of ECM connector and engine coolant temperature sensor connector.
|
Is there poor contact of ECM connector or engine coolant temperature sensor connector?
|
Repair the poor contact of ECM connector or engine coolant temperature sensor connector.
|
|
3.CHECK HARNESS BETWEEN ECM AND ENGINE COOLANT TEMPERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and engine coolant temperature sensor.
3) Measure the resistance of harness between ECM connector and engine coolant temperature sensor connector.
Connector & terminal
(B134) No. 49 — (E8) No. 1:
(B134) No. 67 — (E8) No. 2:
|
Is the resistance less than 1 Ω?
|
|
Repair the harness and connector.
NOTE:
In this case, repair the following item:
• Open circuit in harness between ECM connector and engine coolant temperature sensor connector
• Poor contact of coupling connector
|
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 connector and chassis ground.
Connector & terminal
(B134) No. 49 (+) — Chassis ground (−):
|
Is the voltage 5 V or more?
|
Repair the short circuit of harness to power supply between ECM connector and engine coolant temperature sensor connector.
|
Replace the engine coolant temperature sensor.
|
