The engine coolant temperature sensor is located on the thermostat housing. It is a resistor type sensor which detects the engine coolant temperature. The warm-up state of the engine is judged from the sensor output voltage. When a cold signal is sent to the ECU, the fuel injection amount, idle revolution speed and the injection timing are suitably controlled.
When the coolant temperature sensor is faulty, the engine coolant temperature is regarded as being 176°F (80°C). Because of this, engine starting may be difficult, driveability may become poor and the idle quality may suffer during cold operating conditions. The trouble may not be noticed when the engine is at normal operating temperature.