Basic Information Relating to The Intake Air Temperature Sensor

Basic information of the intake air temperature sensor

The intake air temperature (IAT) sensor is located on the intake pipe or in the air flow meter. It is a two-wire sensor. One is the 5V voltage THA supplied by the engine ECU, and the other one is E2 and the internal ground of the engine. Its function is to detect the intake air temperature of the engine, convert the intake air temperature into a voltage signal, and input it to the ECU as a signal for fuel injection correction. There are different models of IAT sensor, Cummins IAT sensor 2897332, Cummins IAT sensor 4984570, etc.  

Working principle of the intake air temperature sensor 

The IAT sensor is a negative temperature coefficient thermistor. When the temperature rises, the resistance value decreases. When the temperature decreases, the resistance value increases. With the change of resistance in the circuit, the voltage changes, generating different voltage signals to complete the automatic operation of the control system. When the car is cold, the signal of the IAT sensor is basically the same as that of the engine water temperature sensor. When the car is hot, the signal voltage is about 2~3 times that of the water temperature sensor. 

Fault analysis of the intake air temperature sensor

Although the intake temperature sensor can be a fairly unimpressive component, it's still important to look out for symptoms of a faulty IAT sensor. Symptoms caused by the fault include difficulty in starting, unstable idling speed, and excessive exhaust emissions. The longer the problem goes unsolved, the worse the damage becomes over time. The fault analysis of IAT sensor are as follows.

1. If the ground wire of the IAT sensor is not in good contact, the data stream will display abnormally low temperature, and the air density at low temperature will be high, which will increase the fuel injection pulse width and cause the mixed steam to be too thick.

2. If the sensor is short-circuited, the data flow will display abnormally high temperature, and the high-temperature air density will be low, which will reduce the fuel injection pulse width and cause the mixed steam to be too lean.

3. The higher the temperature of the IATsensor, the denser the mixed steam will be. The open circuit of the sensor or poor grounding will cause the mixed steam to be too lean, resulting in difficulty in starting.

Resistance detection

When single-piece detection, put the ignition switch in the OFF position, unplug the wire connector of the IAT sensor, and remove the sensor, heat the IAT sensor with an electric hair dryer, infrared lamp or hot water, and use a multimeter with the ohm range. Measure the resistance value between the two terminals at different temperatures, comparing the measured resistance value with the standard value, if it does not match the standard value, replace the IAT sensor.