Escape 4WD L4-2.5L Hybrid (2009)
Engine Temperature Sensor: Description and Operation
Cylinder Head Temperature (CHT) Sensor
The CHT sensor is a thermistor device in which the resistance changes with temperature. The electrical resistance of a thermistor decreases as the
temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor
terminals and provides electrical signals to the PCM corresponding to temperature.
Thermistor type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so varying the resistance of the
passive sensor causes a variation in total current flow.
The CHT sensor is installed in the aluminum cylinder head and measures the metal temperature. The CHT sensor provides complete engine temperature
information and can be used to infer coolant temperature. If the CHT sensor conveys an overheating condition to the PCM, the PCM then initiates a
fail-safe cooling strategy based on information from the CHT sensor. A cooling system failure such as low coolant or coolant loss could cause an
overheating condition. As a result, damage to major engine components could occur. Using both the CHT sensor and fail-safe cooling strategy, the PCM
prevents damage by allowing air cooling of the engine and limp home capability. For additional information, refer to Powertrain Control Software See:
Computers and Control Systems/Description and Operation/Powertrain Control Software Fail-Safe Cooling Strategy.
Cylinder Head Temperature (CHT) Sensor
