Circuit/System Description

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the ECT signal circuit and a ground for the low reference circuit.

The purpose of this diagnostic is to analyze the performance of the ECT sensor by comparing the response and the range of the sensor signal to two distinct models under various operating conditions.

• The first model verifies that the sensor is not stuck in range.
• The second model verifies that the sensor is within an acceptable operating range of the calculated ECT.

  Both models use various parts of the information derived from the following inputs:

  • Ambient air temperature (AAT)
  • ECT
  • Engine OFF time
  • Engine run time
  • Intake air temperature (IAT)
  • mass air flow (MAF)