P0111 Intake air temperature sensor – signal out of range / performance
DTC Description P0111 General
The IAT sensor (intake air temperature) is a thermistor, which basically means that it measures the air temperature by detecting changes in the resistor’s airflow resistance. It is usually located somewhere in the intake air duct, but in some applications it can be placed in the intake manifold. This is usually a two-wire sensor powered by a 5-volt reference cable (which also acts as a signal cable) with an ECM (powertrain control module) and a ground wire. When the air flows through the sensor, the resistance changes. This change in resistance affects the 5 volts supplied to the sensor, respectively. Colder air results in higher resistance and higher signal voltage, while warmer air results in lower resistance and lower signal voltage. PCM monitors this change in 5 volts and calculates the air temperature. If the ECM detects a voltage outside the normal operating range of the sensor, P0111 will be set.
Causes of general failure code P0111
Depending on the year, brand and model, DTC P0111 can have many causes. Here are some of the most common.
- Defective IAT sensor – As with all semiconductor devices, the IAT sensor may stop working properly due to manufacturing processes or damage.
- Dirty sensor – if the IAT sensor is particularly dirty, for example due to a badly installed air filter or excessive crankcase ventilation (PCV), the sensitivity of the sensor may deteriorate and will not respond so quickly to temperature changes.
- Vehicle storage – vehicles are particularly susceptible to rodent damage. Nesting rodents can bite wires, inter alia, interrupting critical circuits for engine operation.
Diagnosing DTC P0111 is not a particularly difficult task. The sensor itself is easy to use, which facilitates its analysis. On the other hand, if you need to detect a break or short in the wiring harness, it will take some time and patience. Depending on the year, brand and model, the IAT may be at a reasonable price, in many cases cheaper than usd 100, but if it is part of the MAF sensor, the price will increase significantly.