Toyota Corolla Repair Manual: Circuit description

Refer to dtc p0115

Monitor description

The engine coolant temperature (ect) sensor is used to monitor the engine coolant temperature. The ect sensor has a thermistor that varies its resistance depending on the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. The variations in resistance are reflected in the voltage output from the sensor. The ecm monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage deviates from the normal operating range, the ecm interprets this as a fault in the ect sensor and sets a dtc.

Examples:

1.  upon starting the engine, the coolant temperature (ect) was between 35 c (95 °F) and 60 c (140 °F).

   If after driving for 250 seconds, the ect still remains within 3 c (5.4 °F) of the staring temperature, a dtc will be set. (2 Trip detection logic)

2.  upon starting the engine, the coolant temperature (ect) was over 60 c (140 °F). If after driving for 250 seconds, the ect still remains within 1 c (1.8 °F) of the starting temperature, a dtc will be set. (6 Trip detection logic)

Monitor strategy

Typical enabling conditions

Typical malfunction thresholds

Component operating range

Wiring diagram

Refer to dtc p0115