Dodge Durango
 Service Manual
Fuel System » Fuel injection system » Description and operation
Engine coolant temperature sensor-pcm input


The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.

The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.


At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor.

The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return).

When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer airfuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.

The PCM uses inputs from the ECT sensor for the following calculations:

  • for engine coolant temperature gauge operation through CCD or PCI (J1850) communications
  • Injector pulse-width
  • Spark-advance curves
  • ASD relay shut-down times
  • Idle Air Control (IAC) motor key-on steps
  • Pulse-width prime-shot during cranking
  • O2 sensor closed loop times
  • Purge solenoid on/off times
  • EGR solenoid on/off times (if equipped)
  • Leak Detection Pump operation (if equipped)
  • Radiator fan relay on/off times (if equipped)
  • Target idle speed
    More about «Description and operation»:

    Powertrain control module (pcm)

    Modes of operation

    Automatic shutdown (asd) relay sense-pcm input

    Battery voltage-pcm input

    Brake switch-pcm input

    Engine coolant temperature sensor-pcm input

    Five volt sensor supplies-primary and secondary

    Ignition circuit sense-pcm input

    Intake manifold air temperature sensor-pcm input

    Manifold absolute pressure (map) sensor-pcm input

    Oil pressure sensor-pcm input

    Oxygen sensor (o2s)-pcm input

    Power grounds

    Power steering pressure switch- pcm input

    Sensor return-pcm input

    Throttle position sensor (tps)-pcm input

    Vehicle speed and distance-pcm input

    Auto shutdown (asd) relay-pcm output

    Ccd bus (+/-) circuits-pcm outputs

    Data link connector-pcm input and output

    Fuel injectors-pcm output

    Fuel pump relay-pcm output

    Idle air control (iac) motor-pcm output

    Oxygen sensor heater relays-pcm output

    Radiator cooling fan relay-pcm output

    Throttle body

    Dodge Durango Service Manual / Fuel System / Fuel injection system / Description and operation / Engine coolant temperature sensor-pcm input

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