P0115

CIRCUIT DESCRIPTION






The engine coolant temperature sensor is mounted in a coolant passage in a cylinder head. A thermistor built into the engine coolant temperature sensor changes the resistance value according to the engine coolant temperature. The lower the engine coolant temperature, the greater the thermistor resistance value, and the higher the engine coolant temperature, the lower the thermistor resistance value. The engine coolant temp. sensor is connected to the Engine Control Module (ECM) at terminal THW. The (5 volt) power source voltage in the ECM is applied to the engine coolant temp. sensor from the terminal THW via a resistor R. That is, the resistor R and the engine coolant temperature sensor are connected in series. When the resistance value of the engine coolant temperature sensor changes in accordance with changes in the engine coolant temperature, the potential at terminal THW also changes. Based on this signal, the ECM increases the fuel injection volume to improve driveability during cold engine operation.

NOTE: If the ECM records the DTC PO115, it operates the fail safe function in which the coolant temperature is assumed to be 80°C (176°F).

WIRING DIAGRAM

Engine Coolant Temperature Sensor Circuit:

HINT: After confirming DTC PO115 use the OBD II scan tool or LEXUS hand-held tester to confirm the engine coolant temperature from CURRENT DATA.






INSPECTION PROCEDURE
HINT: If DTCs PO110 (Intake air temp. circuit malfunction), PO115 (Engine coolant temp. circuit malfunction), PO120 (Throttle position circuit malfunction) are output simultaneously, E2 (Sensor ground) may be open.



























INSPECTION PROCEDURE
HINT: If DTCs PO115 (Engine coolant temp. circuit malfunction) and PO116 (Engine coolant temp. circuit range/performance) are output simultaneously, engine coolant temp. sensor circuit may be open. Perform troubleshooting of DTC P0115 first.