DTC P0118 Engine Coolant Temperature Circuit High: Wiring Diagram

Engine electrical system, 2.5 L model (without push button start). See appropriate SYSTEM WIRING DIAGRAM article.
Engine electrical system, 2.5 L model (with push button start). See appropriate SYSTEM WIRING DIAGRAM article.

Fig 1: Engine Coolant Temperature - Circuit Diagram (High)
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK CURRENT DATA. Start the engine. Read the value of «Coolant Temp.» using the Subaru Select Monitor or a general scan tool. NOTE: Subaru Select Monitor For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Refer to SUBARU SELECT MONITOR . General scan tool For detailed operation procedures, refer to the general scan tool operation manual.	Is the value of «Coolant Temp.» -40°C (-40°F) or less?	Go to step 2 .	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, temporary open or short circuit of harness may be the cause.
2 CHECK FOR POOR CONTACT. Check for poor contact of ECM and engine coolant temperature sensor connector.	Is there poor contact of ECM or engine coolant temperature sensor connector?	Repair the poor contact of ECM or engine coolant temperature sensor connector.	Go to step 3 .
3 CHECK HARNESS BETWEEN ECM AND ENGINE COOLANT TEMPERATURE SENSOR CONNECTOR. Turn the ignition switch to OFF. Disconnect the connectors from ECM and engine coolant temperature sensor. Measure the resistance of harness between ECM and engine coolant temperature sensor connector. Connector & terminal (B134) No. 30 - (E8) No. 2: (B134) No. 29 - (E8) No. 1:	Is the resistance less than 1 Ω?	Go to step 4 .	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
4 CHECK HARNESS BETWEEN ECM AND ENGINE COOLANT TEMPERATURE SENSOR CONNECTOR. Connect all connectors. Turn the ignition switch to ON. Measure the voltage between ECM and chassis ground. Connector & terminal (B134) No. 30 (+) - Chassis ground (-):	Is the voltage 5 V or more?	Repair the short circuit to power in harness between ECM and engine coolant temperature sensor connector.	Replace the engine coolant temperature sensor. Refer to ENGINE COOLANT TEMPERATURE SENSOR .