Signal Waveform
The ECTS and IATS signals should be smooth and continuous without any sudden changes. When the engine is cold, the ECTS and IATS signals should look similar, depending on the ambient air temperature. After warm-up, the IATS signal should not change significantly, while the ECTS signal should drop. This indicates that the normal increase of the engine coolant temperature is larger than the normal increase of the intake air temperature as the engine warms up.