P0111 - IAT SENSOR 1 CIRCUIT MALFUNCTION

The Intake Air Temperature (IAT) sensor is a thermistor that changes its resistance in response to the engine intake air temperature. This sensor has two wires: 1 is for a 5-volt reference supply from the Powertrain Control Module (PCM), and the remaining wire is ground.

The variation in the reference voltage is monitored by the PCM to determine air temperature. If the intake air is cold, the resistance is high, which results in a high signal voltage. On the other hand, if the intake air temperature is high, the resistance decreases, resulting in a low signal voltage.

The OBDII DTC P0111 means that the PCM observed a change that exceeded the expected limit in a shorter time than expected in the AIT Sensor signal circuit.

• Check Engine light ON.
• The driver may not notice other symptoms.

Reasons for setting the P0111 OBD2 diagnostic code:

• Open in the IAT Sensor signal or ground circuit.
• Short circuit in IAT Sensor.
• Connections between IAT Sensor and PCM may be deficient.
• The Intake Air Temperature (IAT) sensor may be faulty.

To correctly solve faults caused by the P0111 OBDII fault code, try this:

• Measure the resistance at the IAT Sensor terminals using a DVOM on the ohms scale. If there are 0 ohms the circuit is open or shorted, replace the IAT Sensor.
• Check the wiring related to the IAT Sensor. If you find defects in any of these components, repair or replace them.