Monitor Description

Fig 1: Engine Coolant Temperature (ECT) Malfunction Graph

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The ECM estimates the coolant temperature based on starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated coolant temperature reaches 75°C (167°F), the ECM checks the actual ECT. If the actual ECT is less than 75°C (167°F), the ECM will interpret this as a fault in the engine cooling system or thermostat and set a DTC.