Home Sensors Engine Coolant Temperature Sensor
Spreadfirefox Affiliate Button

 

 

Enter your email address:

Diagnostic Kit Poll

What Diagnostic Tool Do you use
 



Sensors
Engine Coolant Temperature Sensor E-mail
The Coolant temperature sensor is often a 2 wire type. It is a Negative Temperature Co efficient Sensor. Meaning when the temperature of the engine increases the Resistance in the sensor decreases.
  • The Coolant sensor is a Resistance circuit. It provides a signal voltage back to the Ecu which is mainly used for fueling. The are the 4 terminal type sensors which are 2 Resistance circuits in 1 sensor. 1 circuit may be used for the Engine control unit and the other may be used for a dashboard temperature gauge or glow plug control unit. Often seen on Vag Group Motors.

    •  

  • The Coolant temperature sensor has a sensor supply voltage which is generally 5 volts and a signal voltage which is generally approx 3.5 volts
Testing with a Volt meter: The supply voltage can be measured as 5 volts. The return voltage (signal voltage) will generally be 3-3.5 volts on a cold engine. As the engine warms up the voltage will decrease to approx .5 volts.

Testing with an Oscilloscope:
 

Measurement taken with a Pico Automotive scope


The Voltage can be seen to decrees as the engine warmes up. There is a different type of sensor fitted to Vauxhall were the supply voltage will step up when the temperature reaches a set point. This is to give the temperature sensor a wider scale and can offer a more fine control by the Ecm.
Faults with the temperature sensor will show up on a scope as era tic peaks or trough's.