P0115

DTC P0115
ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT MALFUNCTION (TW)





Description
The Engine Coolant Temperature Sensor is located on the Engine coolant pipe which is made of aluminum alloy. Its thermistor changes resistance with respect to temperature. A Engine Coolant temperature signal converted into resistance is transmitted to the Engine Control Module (ECM) to control the amount of fuel injection, Ignition timing, Purge Control Solenoid Valve, etc.

DTC Detecting Condition
Immediately at fault recognition.

Trouble Symptom
- Hard to start.
- Erroneous idling.
- Poor driving performance.











1. Connect Subaru Select Monitor or the OBD-II general Scan Tool, and read data.





a. Turn Ignition switch to "OFF".
b. Connect Subaru Select Monitor or the OBD-II General Scan Tool to Data Link Connector.
c. Turn Ignition switch to "ON" and Subaru Select Monitor or OBD-II General Scan Tool switch to "ON".
d. Start Engine.
e. Read data on Subaru Select Monitor or OBD-II General Scan Tool.

Subaru Select Monitor
- Designate mode using function key.
- Function mode: FO5 or FO6.
[CHECK] Is the value greater than 3OO°F with function mode F05?
Is the value greater than 15O°C with function mode F06?
[YES]: Go to step 2.
[NO]: Go to next [CHECK].

[CHECK]: Is the value less than -40°F with function mode F05?
Is the value less than -40°C with function mode F06?
[YES]: Go to step 3.
[NO]: Repair poor contact in connectors or harness.
Engine Coolant Temperature Sensor connector.
ECM connector.
Coupling connector (B21).

OBD-II General Scan Tool
- For detailed operation procedures refer to the OBD-II General Scan Tool instruction Manual.

2. Check harness.





a. Turn Ignition switch to "OFF".
b. Remove Idle Air Control Solenoid Valve by-pass air hose.
c. Disconnect connector from Engine Coolant Temperature Sensor.





d. Connect Subaru Select Monitor or the OBD-II General Scan Tool to Data Link Connector.
e. Turn Ignition switch and Subaru Select Monitor or OBD-II General Scan Tool switch to "ON".
f. Read data on Subaru Select Monitor or the OBD-II General Scan Tool.

Subaru Select Monitor
- Designate mode using function key.
- Function mode: FO5 or FO6.
[CHECK]: Is the value less than -4O°F with function mode F05?
Is the value less than -40°C with function mode FO5?
[YES]: Replace Engine Coolant Temperature Sensor.
[NO]: Repair short circuit of harness between Engine Coolant Temperature Sensor connector and ECM connector.

OBD-II General Scan Tool
- For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.

3. Check harness.





a. Turn Ignition switch to "OFF".
b. Remove Idle Air Control Solenoid Valve by-pass air hose.
c. Disconnect connector from Engine Coolant Temperature Sensor.
d. Turn Ignition switch to "ON".





e. Measure voltage between Engine Coolant Temperature Sensor and body.
[CHECK]: Connector & terminal:
(E8) No. 1 - Body/4 Volts, or more.
[NO]: Repair open circuit of harness or poor contact in ECM and Engine Coolant Temperature Sensor connector.
[YES]: Go to the next step.





f. Turn Ignition switch to "OFF".
g. Measure resistance of harness between Engine Coolant Temperature Sensor connector and body.
[CHECK]: Connector & terminal:
(E8) No. 2 - Body/10 Ohms, or less.
[NO]: Repair open circuit of harness or poor contact in ECM and Engine Coolant Temperature Sensor connector.
[YES]: Replace Engine Coolant Temperature Sensor.