Malfunction Threshold

Malfunction determination 1:

If the difference between the current measured coolant temperature at the radiator (ECT 2) and the initial coolant temperature at the radiator (ECT 2) is at least 46°F (8°C) when the estimated coolant temperature at the engine (ECT 1) reaches 164°F (74°C), a malfunction is detected (thermostat stuck open); or if the coolant temperature at the radiator (ECT 2) only reaches 72°F (22°C), a malfunction is detected (thermostat malfunction).

Malfunction determination 2:

When the estimated engine coolant temperature (ECT 1) reaches 159°F (71°C) before the measured engine coolant temperature (ECT 1) reaches 159°F (71°C), a malfunction is detected.