What Does the P0113 Code Mean?
Diagnostic trouble code P0113 stands for “Intake Air Temperature (IAT) Sensor Circuit High Input.” If your OBD-II scanner reports this code, it means your car’s computer has determined that there’s a problem with the IAT sensor 1 or its circuit.
A working IAT sensor sends its readings to the PCM. Guided by this data, the computer adjusts the fuel injectors and other components that control the internal combustion chamber. Accurate readings help the engine burn fuel efficiently.
When the PCM gets a signal voltage reading above the maximum value, it realizes that the IAT sensor circuit has malfunctioned, either because the sensor is unplugged, the terminals are damaged, one of the sensor wires has been cut, or some other open circuit issue. The computer knows -40 is not the correct reading, so it switches on the Check Engine Light and logs the error code P0113.
What is an Intake Air Temperature (IAT) Sensor and How Can It Cause P0113?
The Intake Air Temperature (IAT) sensor isn’t present on all engines, thus the P0113 code isn’t on some vehicle code lists; some platforms use the Mass Airflow (MAF) sensor to measure incoming air temperature. But no matter how the air temperature is measured, the ECM/PCM needs to know the temperature of the incoming air because cold air has more oxygen molecules per cubic centimeter of air than hot air, and that difference must be factored in for proper air fuel mixture.
The IAT sensor is a two-wire sensor with a negative temperature coefficient resistor positioned so that it reads the air entering the engine. It can be located on the air cleaner, in the air inlet tube, or in the intake manifold.
One of the two wires receives about 4.6 volts from the ECM/PCM and the other wire is a reference ground, also from the ECM/PCM. The reason it’s slightly less than the 5 volts delivered to three wire sensors is that there is a resistor inside the ECM/PCM on each two-wire sensor feed. Because the sensing resistor is negative temperature coefficient, the resistance of the sensor is reduced as it gets warmer. As the resistance goes down, so does the voltage measured at the ECM/PCM. Lower voltage means hotter air.
If the sensor is disconnected or if a wire is chewed or cut leading to the sensor, the voltage registered by the ECM/PCM tops out at 4.6 volts, which is equal to -40 degrees (-40 Fahrenheit is exactly the same as -40 Celsius). This is what you’ll see on the basic OBD2 generic scan tool live datastream. But depending on the manufacturer, the OEM Enhanced datastream can show an entirely different temperature. More about that in a minute.
What Can Happen if I Ignore P0113?
The reason an open IAT sensor won’t usually do anything except illuminating the Check Engine (MIL) light and storing a code is because most ECM/PCM algorithms will substitute a value that usually works. For example, if you unplug the IAT sensor on a 2000s Dodge Truck while looking at the OEM live data, the ECM/PCM won’t show -40 degrees – it’ll show 101 degrees Fahrenheit, which is a reading that will usually enable the vehicle to be driven without damage.
Older vehicles (pre OBD2 and depending on the manufacturer) would sometimes run horrible, with black smoke and no power if the IAT failed. This led the ECM/PCM software engineers to create the fail safe strategy described above.
The problem is that if you ignore the MIL light with a P0113 code and keep driving, and then there’s a sudden cold snap (like a crisp 40 degree morning), the Engine Coolant Temperature (ECT) sensor will be reading 40 degrees F and the IAT will still be reading 101 degrees F. This disparity in air and coolant temperature will typically fool the ECM/PCM into drastically over-fueling the engine during a cold start – meaning it can foul the spark plugs, resulting in an unexpected no-start.
Thus, on the spectrum of OBD-II codes, a P0113 ranges from moderately severe to barely an issue. Again, it all depends on how the ECM/PCM algorithms are set up.
What are the Possible Causes of the P0113 Code?
There are several possible issues that can trigger the P0113 code. Common culprits include the following:
- Intake air temperature sensor 1 experienced an internal problem
- Bad connection between the IAT sensor 1 and its circuit due to problems like dirt, rust, and looseness
- Damaged IAT circuit wiring
- Problem with the mass air flow sensor (if the IAT is integrated into the mass air flow sensor)
- PCM issues (such as software in need of an update, but this is very VERY rare.)
What are the Common Symptoms of the P0113 Code?
The most likely symptoms of the code P0113 include:
- No symptoms at all except a Check Engine Light
- No-start with a gas smell on a cold snap morning.
Again, when code P0113 is set, the engine can also display other symptoms such as difficulties in cold starts. The exact symptoms can vary depending on the manufacturer, so a P0113 in a Ford vehicle may present slightly differently in a Nissan with a P0113.
How to Test the IAT Sensor
You have to be able to access the sensor first.
With the sensor disconnected and the key switched on (engine off), measure the voltage at the sensor – be careful not to damage the terminals. You should see 4.6 volts with the sensor disconnected. If you do, use a digital volt-ohmmeter to measure sensor resistance at the sensor itself (key on or off, it doesn’t matter). If the sensor is wide open (no continuity in any range), the sensor is bad.
If you don’t get the 4.6 volts, there could be a wiring problem – do a visual inspection and if you don’t see anything, hire a mechanic to find and fix the problem.
How to Diagnose the P0113 Code
Finding the root cause of an OBD-II trouble code can be difficult as there are a lot of factors to take into account, as well as several possible causes. The engine code P0113 alone has a handful of possible culprits, as listed above.
The video below can help you get an idea of how to troubleshoot this particular code:
How to Fix the P0113 Code
Because OBD-II codes have several possible causes, there’s no one way to fix a specific code. With each possible cause comes specific solutions and fixes, which is why it’s essential to diagnose OBD-II codes correctly and find out the exact cause before attempting any repairs.
With that said, only drivers with sufficient technical knowledge should attempt DIY fixes on an engine with a P0113 code. Otherwise, bring the vehicle to the nearest auto repair shop and get a trained professional to replace the ailing IAT sensor.
If you do decide to tackle the P0113 fix yourself, keep in mind that different types of vehicles may require their own distinct solutions—so always check the owner’s manual and consult the factory repair information for your application.
Repair manuals, such as those from Chilton, are useful, but an ALLDATA subscription is even better. ALLDATA has single-vehicle subscriptions for DIYers that provide detailed factory repair information.
It’s also worth noting that not every instance of a P0113 trouble code requires replacement of the IAT sensor. The fault may lie in other parts of the IAT circuit, such as the connection. If the sensor is faulty, a replacement part can cost anywhere between $1.94 to $110.93 on CarParts.com.
Other Notes About Code P0113
There are other diagnostic trouble codes that cover the IAT sensors and their attendant circuitry. For example, an intermittent IAT sensor signal falls under P0114. Meanwhile, a sensor that produces a low voltage input merits the trouble code P0112.
P0098 is the mirror image of P0113 since it reports the same issue of low temperature, higher electrical resistance, and high signal voltage in sensor 2, the second IAT sensor in the engine.
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