What occurs with a low temperature IAT (Intake Air Temperature) and ECT (Engine Coolant Temperature)?

A low temperature reading for both Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) indicates that the engine is running in a colder environment. When the IAT is low, the engine control unit (ECU) interprets the air entering the engine as denser and possibly more oxygen-rich. Simultaneously, a low ECT suggests that the engine has not reached its optimal operating temperature.

When the ECU detects these low temperature readings, it tends to add more fuel to the air-fuel mixture to compensate for the denser air and ensure proper combustion at lower temperatures. This results in a richer air-fuel mixture, as the increased fuel helps to overcome the effects of the colder conditions and support smooth engine performance.

This rich condition is necessary for preventing misfires, ensuring proper combustion, and maintaining engine function while the engine is still warming up. Therefore, the correct answer takes into account that both the IAT and ECT readings contribute to the ECU's adjustment of the fuel mixture to counteract the effects of low temperatures.