Troubleshooting

CIRCUIT DESCRIPTION
A thermistor built into the engine coolant temperature sensor changes the resistance value according to the engine coolant temperature.
The structure of the sensor and connection to the ECM is the same as in the intake air temperature circuit malfunction.
If the ECM detects the DTC P0115, it operates fail-safe function in which the engine coolant temperature is assumed to be 80 °C (176 °F).

Step 1:

Step 2:

INSPECTION PROCEDURE

HINT:
- If DTCs P0115 and P0116 are output simultaneously, engine coolant temp. sensor circuit may be open. Perform troubleshooting of DTC P0115 first.
- Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.