Subaru Workshop Service and Repair Manuals

ECU/Coolant Temperature Sensor Harness Testing

CHECK ECU VOLTAGE

1.

Turn ignition "ON" (engine "OFF").

2.

Check ECU voltage between the following connector terminals:

Connector:

Terminal:

Voltage:

F121

5-1

0.15-4.85V

F121

5-2

0.15-4.85V

CHECK HARNESS BETWEEN ECU AND TEMPERATURE SENSOR

1.

Disconnect ECU connector.

2.

Measure resistance between ECU connector and sensor connector:

Connector & terminal:

Resistance:

(F121)5-(F22)2

Below 1 Ohm

(F121)1-(F22)1

Below 1 Ohm

(F121)2-(F22)1

Below 1 Ohm

3.

Measure resistance between ECU connector and terminal (F121)5 and ground.  Reading should be infinite.

Coolant Temperature Sensor Testing

CHECK COOLANT TEMPERATURE SENSOR

1.

Disconnect coolant temperature sensor connector.

2.

Measure resistance between sensor terminals 1 and 2 (sensor side):

Resistance:

Temperature: 

2 - 3K Ohms

20° C (68° F)

270 - 370 Ohms

80° C (176° F)