Escape, Mariner 2008-2009

Cylinder Head Temperature Sensor

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Location



4-Cylinder Engine

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

The Cylinder Head Temperature (CHT) sensor is located between the two center ignition coils.

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Fig. Cylinder Head Temperature (CHT) sensor location-except hybrid



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Fig. Cylinder Head Temperature (CHT) sensor location-hybrid

6-Cylinder Engine

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

The Cylinder Head Temperature (CHT) sensor is located at the front of the right cylinder head.

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Fig. Cylinder Head Temperature (CHT) sensor location-3.0L engines

Operation



Specific to:

Ford Escape 2005-2008

Mercury Mariner 2005-2008

The Cylinder Head Temperature (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 that 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 can provide 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.

The MECT sensor is a thermistor device in which 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. A thermistor type sensor is considered a passive sensor. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor. The MECT provides motor electronics coolant system temperature information to the PCM. The PCM uses this information for determining when to activate the cooling system fans and indicate over-temperature.

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

The Cylinder Head Temperature (CHT) Sensor is a Negative Temperature Coefficient (NTC) Thermistor that monitors the cylinder head temperature. The CHT Sensor operates within a 5 volt DC reference range, and provides a linear input signal to the Powertrain Control Module (PCM) that is based upon the measured cylinder head temperature.

Removal & Installation



Specific to:

Ford Escape 2005-2008

Mercury Mariner 2005-2008

  1. Detach the Cylinder Head Temperature (CHT) sensor cover and position aside.
  2.  
  3. Disconnect the CHT sensor electrical connector.
  4.  
  5. Remove and discard the CHT sensor.
  6.  
  7. To install, reverse the removal procedure and tighten the CHT sensor to 9 ft. lbs. (12 Nm).
  8.  

4-Cylinder Engine

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

  1. Detach the Cylinder Head Temperature (CHT) sensor cover and position aside.
  2.  
  3. Disconnect the CHT sensor electrical connector.
  4.  
  5. Remove and discard the CHT sensor.
  6.  
  7. To install, reverse the removal procedure and tighten the CHT sensor to 106 inch lbs. (12 Nm).
  8.  

2.3L Engine

Specific to:

Ford Escape 2005-2008

Mercury Mariner 2005-2008


NOTE
This sensor is also referred to as the Cylinder Head Temperature (CHT) sensor

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the cylinder head temperature sensor cover and position aside.
  4.  
  5. Disconnect the cylinder head temperature sensor connector.
  6.  
  7. Remove cylinder head temperature sensor.
  8.  
  9. To install, reverse the removal procedure.
  10.  
  11. Tighten sensor to 9 ft. lbs. (12 Nm).

    Click image to see an enlarged view

    Fig. Cylinder head temperature sensor view -2.3L engine

  12.  

6-Cylinder Engine

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009


NOTE
If the cylinder head is being replaced, the CHT must be replaced.

  1. Disconnect the Cylinder Head Temperature (CHT) sensor electrical connector.
  2.  
  3. Remove the CHT sensor.
  4.  
  5. To install, reverse the removal procedure and not the following:
  6.  
  7. Tighten the CHT sensor to 97 inch lbs. (11 Nm).
  8.  

3.0L Engine

Specific to:

Ford Escape 2005-2008

Mercury Mariner 2005-2008

  1. Drain the cooling system.
  2.  
  3. Disconnect the Engine Coolant Temperature (ECT) sensor electrical connector.
  4.  
  5. To remove the ECT sensor, pull up on locking tab and rotate the sensor clockwise.
  6.  
  7. To install, reverse the removal procedure.
  8.  

Testing



Specific to:

Ford Escape 2005-2008

Mercury Mariner 2005-2008

On applications that do not use an Engine Coolant Temperature (ECT) sensor, the Cylinder Head Temperature (CHT) sensor is used to determine the engine coolant temperature. To cover the entire temperature range of both the CHT and ECT sensors, the PCM has a dual switching resistor circuit on the CHT input. A graph showing the temperature switching from the COLD END line to the HOT END line, with increasing temperature and back with decreasing temperature is included. Note the temperature to voltage overlap zone. Within this zone it is possible to have either a COLD END or HOT END voltage at the same temperature. For example, at 90°C (194°F) the voltage could read either 0.60 volt or 3.71 volts. Refer to the table for the temperature to voltage expected values.

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Fig. Cylinder Head Temperature (CHT) temperature-to-voltage table

  1. Turn the ignition switch to the OFF position.
  2.  
  3. Disconnect the CHT sensor electrical connector.
  4.  
  5. Measure the resistance between CHT + pin 1 and CHT - pin 2 on sensor side of connector.
  6.  
  7. If resistance is not within specification replace sensor.

    Click image to see an enlarged view

    Fig. Cylinder head temperature sensor connector-2.3L hybrid engine

  8.  

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009


NOTE
Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.

2.3L Engine

Specific to:

Ford Escape 2005-2008

Mercury Mariner 2005-2008

On applications that do not use an Engine Coolant Temperature (ECT) sensor, the Cylinder Head Temperature (CHT) sensor is used to determine the engine coolant temperature. To cover the entire temperature range of both the CHT and ECT sensors, the PCM has a dual switching resistor circuit on the CHT input. A graph showing the temperature switching from the COLD END line to the HOT END line, with increasing temperature and back with decreasing temperature is included. Note the temperature to voltage overlap zone. Within this zone it is possible to have either a COLD END or HOT END voltage at the same temperature. For example, at 90°C (194°F) the voltage could read either 0.60 volt or 3.71 volts. Refer to the table for the temperature to voltage expected values.

Click image to see an enlarged view

Fig. Cylinder Head Temperature (CHT) temperature-to-voltage table-2.3L engine

  1. Turn the ignition switch to the OFF position.
  2.  
  3. Disconnect the CHT sensor electrical connector.
  4.  
  5. Measure the resistance between CHT + pin 1 and CHT - pin 2 on sensor side of connector.
  6.  
  7. If resistance is not within specification replace sensor.

    Click image to see an enlarged view

    Fig. CHT sensor connector-2.3L engine

  8.  

CHT Sensor Strategy

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

The CHT Sensor provides a linear input signal to the Powertrain Control Module (PCM) in order to more closely monitor the engine temperature at the cylinder head(s). The CHT signal is compared with Engine Coolant Temperature (ECT) and Engine Oil Temperature (EOT) in order to monitor consistent engine temperatures over a variety of measured operating conditions.

Connection And Wiring Diagnosis

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.  

Many intermittent open or short circuits may be caused by wiring harness and connector movement due to vibration, engine torque, bumps and rough pavement, etc.

  1. Test the wiring harness and connectors by performing the following tests:

    Move the related connectors and wiring while monitoring the appropriate scan tool data.  
     
    Move the related connectors and wiring with the component commanded ON and OFF. Using a suitable the scan tool, observe the component operation.
     
    With the engine running, move the related connectors and wiring while monitoring component operation.
     
    If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary.
     

  2.  
  3. Test the connector terminal pins and/or wiring by performing the following tests:

    Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body.  
     
    Inspect for improperly formed or damaged terminals and test for incorrect terminal tension.  
     
    Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body.  
     
    Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and/or brittle sections of wire in the suspect circuits.  
     
    Inspect for wires that are broken inside the insulation by gently pulling on suspect sections of wiring.
     

  4.  

Ct Circuit Testing

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009

Use a suitable scan tool, a Graphing Multi-Meter (GMM), or a Digital Volt-Ohm Meter (DVOM) in order to view the CHT data.  

CHT Sensor logic is relative to the scale of resistance: when the coolant temperature is low, the voltage is increased. When the coolant temperature is high, the voltage is decreased.

Use a suitable pyrometer or thermometer, as well as visual observation to verify that no air flow, cooling system, or mechanical conditions exist. If an external system fault is evident, repair as required before continuing.  

If a DVOM is being used, additional information may be acquired by taking measurements at the sensor connector as well as the PCM connector. If a significant voltage drop is measured (greater than 0.5 volts DC), check the wiring harness and connections for corrosion, poor pin connections, or damaged wires.

If all engine wiring and pin connections are confirmed, disconnect the CHT Sensor to verify the signal with a DVOM, and verify PCM communication before replacing the CHT Sensor.

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Fig. CHT Sensor Range Chart

Related Diagnostic Trouble Codes

Specific to:

Ford Escape 2008-2009

Mercury Mariner 2008-2009



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Fig. Related Diagnostic Trouble Codes

 
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