DTC P0197 Engine Oil Temperature Sensor "A" Circuit Low: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

• Hard to start
• Improper idling
• Poor driving performance

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

Fig 1: Engine Oil Temperature Sensor A Circuit Low - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

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

   Is the value of [Engine Oil Temperature] 150°C (302°F) or more?

   • 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.
     NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2. CHECK HARNESS BETWEEN ECM AND ENGINE OIL TEMPERATURE SENSOR CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connectors from the engine oil temperature sensor.
   3. Disconnect the connector from ECM.
   4. Measure the resistance between ECM connector and chassis ground.

   Connector & terminal 

   (B135) No. 18 - Chassis ground:

   Is the resistance 1 MΩ or more?

   • Yes: Replace the engine oil temperature sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>Engine Oil Temperature Sensor .
   • No: Repair the short circuit to ground in the harness between the ECM connector and engine oil temperature sensor connector.