DTC P0198 Engine Oil Temperature Sensor High: Notes

DTC DETECTING CONDITION: 

Immediately at fault recognition

TROUBLE SYMPTOM: 

• Hard to start
• Improper idling
• Poor driving performance

WIRING DIAGRAM: 

• Engine Electrical System NON-TURBO MODEL (WITHOUT PUSH BUTTON START) Ref. to WIRING SYSTEM > Engine Electrical System >  NON-TURBO MODEL (WITHOUT PUSH BUTTON START)  .
• Engine Electrical System NON-TURBO MODEL (WITH PUSH BUTTON START) Ref. to WIRING SYSTEM > Engine Electrical System >  NON-TURBO MODEL (WITH PUSH BUTTON START)  .

1. CHECK CURRENT DATA  .
   1. Start the engine.
   2. Using the Subaru Select Monitor, read the value in [Oil Temperature].
   NOTE: For detailed operation procedures, refer to "READ CURRENT DATA FOR ENGINE". Ref. to ENGINE (DIAGNOSTICS) (H4DO) >  Subaru Select Monitor   .

   Is the value of [Oil Temperature] -40°C (-40°F) or less?

   Yes: Go to   2  .

   No: 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 between the ECM and engine oil temperature sensor connectors.

   Is there poor contact of the ECM or engine oil temperature sensor connectors?

   Yes: Repair the poor contact of ECM or engine oil temperature sensor connector.

   No: Go to   3  .

3. CHECK HARNESS BETWEEN ECM AND ENGINE OIL TEMPERATURE SENSOR CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connectors from the ECM and engine oil temperature sensor.
   3. Measure the resistance of the harness between the ECM connector and engine oil temperature sensor connector.

      Connector & terminal 

      (B134) No. 20 - (E75) No. 2:

      (B134) No. 29 - (E75) No. 1:

   Is the resistance less than 1 Ω?

   Yes: Go to   4  .

   No: Repair the harness and connector.

   NOTE: In this case, repair the following item:

   • Open circuit in harness between ECM connector and engine oil temperature sensor connector
   • Poor contact of coupling connector
4. CHECK HARNESS BETWEEN ECM AND ENGINE OIL 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. 20 (+) - Chassis ground (-):

   Is the voltage 5 V or more?

   Yes: Repair the short circuit to power in harness between ECM connector and engine oil temperature sensor connector.

   No: Replace the engine oil temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO) >  ENGINE OIL TEMPERATURE SENSOR  .