Engine Coolant Temperature Sensor

Temperature sensor is temperature sensitive semiconductor resistor, which usually has negative temperature coefficient (NTC), meaning that the resistance goes down with increasing temperature. The opposite type – positive (PTC) is very rare.

Coolant temperature sensor
Engine coolant temperature sensor

Application:

  • Engine coolant temperature sensor
  • Air temperature sensor
  • Oil temperature sensor
  • Fuel temperature sensor
ECT location
Typical location of the engine coolant temperature sensor
Connection to ECT
Connection of the USB Autoscope IV to the sensor signal wire
Setting the USB Autoscope IV to the temperature sensor testing mode
Setting the USB Autoscope IV to the temperature sensor testing mode
Output voltage waveform of the engine coolant temperature sensor in good condition
Output voltage waveform of the engine coolant temperature sensor in good condition on Mitsubishi Lancer 1.6 2005, recorded while the engine was cold and running at idle
Waveform ECT
Output voltage waveform from a properly functioning engine coolant temperature sensor. Output voltage of an NTC sensor decreases with increasing temperature, due to the way the circuit is designed.
ECT-connection-circuit
Output voltage waveform of the engine coolant temperature sensor with a malfunction
Output voltage waveform of the engine coolant temperature sensor with a malfunction, recorded while the engine was cold and running at idle
Malfunctioning ECT waveform
Output voltage waveform from a malfunctioning engine coolant temperature sensor.
Malfunctioning ECT waveform
The sensor circuit develops an intermittent connection as the sensor heats up.
malfunctioning ECT waveform
Output voltage waveform from a malfunctioning engine coolant temperature sensor

Video

Waveform examples