DTC P0198 Engine Oil Temperature Sensor High: Wiring Diagram

Fig 1: Engine Oil Temperature Sensor Wiring Diagram (High)

Courtesy of SUBARU OF AMERICA, INC.

Step	Check	Yes	No
1 CHECK CURRENT DATA. Start the engine. Read the data of the oil temperature sensor signal using the Subaru Select Monitor or 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 oil temperature less than -40°C (-40°F)?	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 oil temperature sensor connector.	Is there poor contact of ECM or oil temperature sensor connector?	Repair the poor contact of ECM or the oil temperature sensor connector.	Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND OIL TEMPERATURE SENSOR CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector from ECM and oil temperature sensor. Measure the resistance of the harness between ECM and oil temperature sensor connector. Connector & terminal (B137) No. 21 - (E75) No. 2: (B134) No. 29 - (E75) 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 oil temperature sensor connector Poor contact of coupling connector
4 CHECK HARNESS BETWEEN ECM AND OIL TEMPERATURE SENSOR CONNECTOR. Connect all connectors. Turn the ignition switch to ON. Measure the voltage between ECM and chassis ground. Connector & terminal (B137) No. 21 (+) - Chassis ground (-):	Is the voltage 5 V or more?	Repair the short circuit to power supply in harness between ECM and oil temperature sensor connector.	Replace the oil temperature sensor. Refer to OIL TEMPERATURE SENSOR Oil Temperature Sensor.