Signal Wave Form & Data

This figure shows the wave form at terminal 3 of IATS at idle RPM.

Fig 1: Identifying Signal WAVE FORM

Courtesy of HYUNDAI MOTOR CO.

1. The lower the temperature is, the closer the output voltage of IAT goes to 5 V.

   In case, when engine is warmed up, the output is 5 V.

   Possible cause: Open signal and ground line, or sensor's inner circuit open

2. In case, when engine is cold, the output is below 0.5V.

   Possible cause: Short between signal and ground line Bad PCM

   The IATS and ECTS signals should be smooth and continuous without any sudden changes. When the engine is cold, the IATS and ECTS signals should look similar, depending on the ambient air temperature. After warm-up the IATS signal should not change significantly, while 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.