Coolant temperature sensor (CTS) is a semiconductor device thermistor, the electrical resistance of which changes with changes in ambient temperature

DTOZH is installed in the thermostat housing.

By the resistance of the sensor, the ECU estimates the thermal conditions of the engine

The data obtained is used to calculate most control commands for elements of the engine control system, as well as to turn on the electric fan of the engine cooling system.

If the DTOZH malfunctions, the electronic control unit switches the system to backup mode.

With the ignition off, disconnect the engine management system wiring harness block from the coolant temperature sensor.

The terminals of the block “A” and “B” are marked on its body.

How to check the coolant sensor

Connecting the tester probes to terminal “B” of the block and to the engine “ground”, with the ignition on, measure the voltage of the sensor input signal circuit.

How to check the coolant sensor

The device should detect a voltage of 4.8-5.2 V.

If the voltage does not match, check the serviceability of the circuit (open and short to ground) between terminal “B” of the wiring harness block and terminal “39” of the controller.

If the circuit is OK, the controller is faulty.

How to check the coolant sensor

By connecting the tester probes to terminal “A” of the block and to the “ground” of the engine, we measure the resistance.

Sensor resistance values at different coolant temperatures

If the sensor grounding circuit is working properly, the device should register a resistance of less than 1 ohm.

The cause of increased resistance may be an unreliable connection in the pads connected to the sensor or controller.

To check the sensor, disconnect the engine control system wiring harness block from it.

We use a tester to measure the resistance of the sensor for two values of coolant temperature - cold and warm engine.

Compare the obtained values with the control ones.

If the measured resistance values do not match the control values, the sensor must be replaced.

Coolant temperature, ° C = Resistance Ohm

  • 100=180
  • 90=240
  • 80=330
  • 70=470
  • 60=670
  • 50=970
  • 45=1200
  • 40=1460
  • 35=1800
  • 30=2240
  • 25=2800
  • 20=3520
  • 15=4450
  • 10=5670
  • 0=9420