How To Test: P0113 OBD II Trouble Code (Honda 2.2L, 2.3L)

OBD II trouble code P0113 IAT Sensor Circuit High Voltage usually points to one of two things, either a failed intake air temperature (IAT) sensor or an open-circuit problem in the sensor's wiring.

The end result of either failure is the PCM thinking that the outside air, the engine is breathing, is around -4°F (-20°C) when the ambient air temperature is anything but that cold!

In this tutorial, I'm gonna' go into the specifics of why your Honda sets a P0113 trouble code and, more importantly, I'm gonna' show you how to test the IAT sensor in a step-by-step way.

P0113 Basics You Need To Know

Your Honda's fuel injection computer (known in tech speak as the PCM = Powertrain Control Module) needs to know the temperature of the air, that the engine is breathing, to inject the correct amount of fuel.

This is where the IAT sensor comes into play since its job is to measure the temperature of the air entering the engine and then report this temperature value to the PCM.

In a nutshell and without getting too technical, the PCM injects less fuel if it senses, via the IAT sensor, that the incoming air is warm. If the incoming air is colder, the PCM now knows to inject more fuel so as to make the air/fuel mixture richer.

Now, when a code P0113 IAT Sensor Circuit High Voltage lights up the check engine light (CEL) on your Honda's instrument cluster, the PCM is letting you know that it's receiving a temperature value of -4°F (-20°C) from the intake air temperature (IAT) sensor and that this temperature value does not vary thru' out the engine's entire operating range.

Briefly, this is how the intake air temperature (IAT) sensor works:

1. The intake air temperature (IAT) sensor is a 2 wire sensor.
   1. One wire (circuit) supplies power.
      • Power is in the form of 5 Volts DC and is provided only with Key On Engine Off (KOEO) or Key On Engine Running (KOER).
      • Power is provided by the PCM.
   2. The other wire (circuit) supplies Ground.
      • This Ground is fed to the IAT sensor by the PCM (internally).
2. The IAT sensor is a resistor (thermistor). Its resistance changes in response to changes in the air's temperature.
   • The cooler the air, the higher the resistance of the IAT sensor.
   • The warmer the air, the lower the resistance of the IAT sensor.
3. When the 5 Volts pass through the intake air temperature (IAT) sensor, the resistance of the sensor produces a voltage drop. This in plain English means that only a certain amount of the 5 Volts are let through to the Ground wire.
   1. The cooler the air is, the less voltage is let thru' onto the Ground wire (due to the IAT sensor's higher resistance).
      • The PCM translates this higher voltage drop into a colder temperature value.
   2. The warmer the air, the more voltage is let thru' onto the Ground wire (due to the IAT sensor's lower resistance).
      • The PCM translates this lower voltage drop into a warmer/hotter temperature value.

So the thing to remember/know, when a P0113 IAT Sensor Circuit High Voltage is stored in the PCM's memory, is that the intake air temperature (IAT) sensor is reporting an extremely high voltage drop (think IAT sensor disconnected from its connector which would not let any of the 5 Volts thru').

And that the PCM interprets this condition as an extremely cold air temperature (-4°F or colder).

Symptoms Of A P0113 Diagnostic Trouble Code

The PCM uses the engine's incoming air temperature input from the IAT sensor to calculate the air/fuel mixture (along with a host of other sensor inputs).

When the IAT sensor fails (or there's a problem with its circuits), your Honda isn't gonna' run/perform optimally.

You may see one or more of the following symptoms when the intake air temperature (IAT) sensor fails:

1. Check engine light (CEL) is on.
2. DTC P0113 is present.
3. Won't pass the state mandated emissions test.
4. Gas mileage will suffer.
5. Rough idle.
6. Hard start and/or extended cranking time.
7. Black smoke coming out of the tailpipe.

Let's find out what are the common causes of a P0113 DTC, in the next subheading.

Common Causes Of A P0113 Trouble Code

Here are the most common causes of a P0113 diagnostic trouble code (DTC):

1. A bad intake air temperature sensor.
2. The intake air temperature sensor wires have an open-circuit problem.
   • This is usually due to human error (like when the engine is replaced and the IAT sensor's connector or wires are damaged).
3. A bad PCM (Powertrain Control Module = Fuel Injection Computer).
   • This is very rare, but it does happen.

With this basic info under our belts, let's turn the page and get testing!