PT Cruiser, 2001 - 2005

Engine Coolant Temperature (ECT) Sensor

Print

Description & Operation



1.6L

The engine coolant temperature (ECT) sensor threads into the rear of the cylinder head, just below the thermostat housing. The ECT Sensor is a Negative Thermal Coefficient (NTC) sensor.

Click image to see an enlarged view

Fig.

The ECT sensor provides an input to the PCM. As temperature increases, resistance of the sensor decreases. As coolant temperature varies, the ECT sensor resistance changes resulting in a different voltage value at the PCM ECT sensor signal circuit. The ECT sensor provides input for various PCM operations. The PCM uses the input to control air-fuel mixture, timing, and radiator fan on/off times. The ECT sensor input is also used for temperature gauge operation.

2.0L & 2.4L

The coolant sensor threads into the front of the cylinder head near the radiator fill tube. New sensors have sealant applied to the threads.

The ECT Sensor is a Negative Thermal Coefficient (NTC), dual range Sensor. The resistance of the ECT Sensor changes as coolant temperature changes. This results in different input voltages to the PCM. The PCM also uses the ECT Sensor input to operate the low and high-speed radiator cooling fans.

Click image to see an enlarged view

Fig.

The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases. As coolant temperature varies, the coolant temperature sensor resistance changes resulting in a different voltage value at the PCM engine coolant sense circuit.

When the engine is cold, the PCM will provide slightly richer air-fuel mixtures and higher idle speeds until normal operating temperatures are reached.

The combination coolant temperature sensor has two elements. One element supplies coolant temperature signal to the PCM. The other element supplies coolant temperature signal to the instrument panel gauge cluster. The PCM determines engine coolant temperature from the coolant temperature sensor.

As coolant temperature varies the coolant temperature sensors resistance changes resulting in a different input voltage to the PCM and the instrument panel gauge cluster. When the engine is cold, the PCM will provide slightly richer air- fuel mixtures and higher idle speeds until normal operating temperatures are reached.

The PCM has a dual temperature range program for better sensor accuracy at cold temperatures. At key-ON the PCM sends a regulated 5-volt signal through a 10,000-ohm resistor to the sensor. When the sensed voltage reaches approximately 1.25 volts the PCM turns on the transistor. The transistor connects a 1,000-ohm resistor in parallel with the 10,000-ohm resistor. With this drop in resistance the PCM recognizes an increase in voltage on the input circuit.

 
label.common.footer.alt.autozoneLogo