Protege 1999-2000

Engine Coolant Temperature Sensor

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Operation



Specific to:

Mazda Protege 1999-2003

The coolant temperature sensor is a variable resistor that is influenced by temperature. Which means, as the temperature changes, so does the resistance inside the sensor. The computer reads this change in resistance to determine the operating temperature of the engine. It uses this reading to determine proper air/fuel mixture and ignition timing settings.

Removal & Installation



1.6L Engine
  1. Drain the engine coolant.
  2.  
  3. Disconnect the ECT sensor connector.
  4.  
  5. Remove the ECT sensor using the special socket (49 D015 004, or equivalent).
  6.  
  7. Replace the gasket.
  8.  
  9. Install in the reverse order of removal.
  10.  
  11. Tighten the ECT sensor to 12-17 ft. lbs. (16-23 Nm).
  12.  
  13. Refill the engine coolant.

    Click image to see an enlarged view

    Fig. Removing the ECT sensor-1.6L engine

  14.  

Testing



Specific to:

Mazda Protege 1999-2003

Mazda Protege5 2002-2003

  1. Before servicing the vehicle, refer to the precautions section.
  2.  
  3. Drain and recycle the engine coolant.
  4.  
  5. Remove the coolant temperature sensor.
  6.  
  7. Place the sensor in a container of water with a temperature approximately 20 degrees C (68 F).
  8.  
  9. Using an ohmmeter, check resistance between the terminals. The resistance should be 2.2-2.6 Kohms.
  10.  
  11. Raise the temperature of the container of water to approximately 80 degrees C (176 F).
  12.  
  13. Using an ohmmeter, check resistance between the terminals. The resistance should be 0.29-0.34 Kohms.
  14.  
  15. If the resistance is not as specified, replace the sensor.
  16.  

Specific to:

Mazda Protege 1999-2003

  1. Remove the ECT.
  2.  
  3. Place the sensor in water with a thermometer and heat the water gradually.
  4.  
  5. Measure the resistance of the sensor and compare to the following values:

    68°F (20°C)-35.5-39.2 kohms
     
    140°F (60°C)-7.18-7.92 kohms
     

  6.  
  7. If not as specified, replace the ECT.
  8.  
  9. If within specification, check wiring harness and connectors between ECT and PCM.
  10.  

Connection & Wiring Diagnosis

Specific to:

Mazda Protege 1998-2003

Mazda Protege5 2002-2003

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.  

ECT Circuit Testing

Specific to:

Mazda Protege 1998-2003

Mazda Protege5 2002-2003

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

ECT 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 the cooling system is operating properly. If a cooling 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 ECT Sensor to verify the signal with a DVOM, and verify PCM communication before replacing the ECT Sensor.

Click image to see an enlarged view

Fig. ECT Sensor Range Chart

ECT Sensor Strategy

Specific to:

Mazda Protege 1998-2003

Mazda Protege5 2002-2003

The ECT Sensor provides a linear input signal to the Powertrain Control Module (PCM) for a number of engine control system calculations. The ECT signal is compared with Manifold Absolute Pressure (MAP), Mass Air Flow (MAF), Intake Air Temperature (IAT), and Fuel Trim (HO2S) in order to determine the correct air-fuel mixture for measured operating conditions. In some cases the ECT Sensor input is used in concert with the A/C Pressure (ACP) Sensor input in order to determine cooling fan and A/C system operation.

Related Diagnostic Trouble Codes

Specific to:

Mazda Protege 1998-2003

Mazda Protege5 2002-2003



Click image to see an enlarged view

Fig. Related Diagnostic Trouble Codes

 
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