On-board diagnostic (OBD) codes are designed to help you or your mechanic identify possible issues in your car. They can be retrieved with a scan tool, though knowing what they mean is another thing. Before attempting any fixes to resolve them, you should first understand the meaning, triggers, and symptoms of the logged code.
What Does the P0111 Code Mean?
Diagnostic trouble code (DTC) P0111 stands for “Intake Air Temperature Sensor 1 Circuit Range/Performance (Bank 1).” This error code is logged when the powertrain control module (PCM) perceives the signal from the intake air temperature (IAT) sensor to be outside factory specifications. Usually, the PCM determines this by comparing the IAT signal to the signal from the engine coolant temperature (ECT) sensor.
The sensor 1 portion of the code applies to vehicles that have multiple IAT sensors. Bank 1 points to the side of the engine opposite the #1 cylinder.
The IAT sensor is a thermistor. Its resistance decreases as its temperature increases. As the temperature rises, the sensor becomes more electrically conductive. It is usually a two-wire sensor that has one wire supplying voltage to the PCM, while the other is a ground.
So when the intake air is cold, it means both the resistance and signal voltage are high. And if the air is warm, then both the resistance and signal voltage is low. The trouble code is set once the PCM detects erratic behavior from the IAT sensor. One example is when there is a huge difference between signals on the IAT signal circuit in a short amount of time.
This error code can also be logged when the PCM recognizes that the signal from the IAT has exceeded the appropriate range when compared to the signal from the ECT sensor.
Note: The definition of code P0111 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.
What are the Possible Causes of the P0111 Code?
P0111 is a generic code, so it can have several triggers. Here are the most common:
- Faulty IAT sensor
- Bad mass air flow sensor (sometimes the IAT is integrated into the MAF)
- Circuit/wiring issues
- Failed PCM
What are the Common Symptoms of the P0111 Code?
You may notice the following symptoms if you drive a car that has a logged P0111 error code:
- Active check engine light
- Bad fuel mileage
- Poor engine performance
How to Diagnose the P0111 Code
Code P0111 should be resolved immediately to avoid complications. However, diagnosing it can be difficult as it has many possible triggers. To make sure you’re on the right path, the diagnostic and repair steps should always depend on the specifications of your vehicle.
Because all cars are built differently, they would also require different diagnoses. A P0111 on a Honda Fit, for instance, may require an entirely different testing process from a P0111 on a Dodge Ram. Refer to a repair manual specific to your vehicle for the appropriate diagnostic steps.
But if you feel like your automotive know-how is lacking, it would be best to let a mechanic troubleshoot this error code instead.
How to Fix the P0111 Code
Code P0111 may be set in vehicles of varying makes and models. It may also share similar triggers and symptoms with other DTCs. There is no one-size-fits-all solution for this code, as different manufacturers require varying solutions.
Always refer to the factory repair information specific to your car before DIY-ing any repairs. But if you aren’t confident in your automotive repair skills, it may be wise to leave the diagnosis and repair to the experts.