P0113 – Intake air temperature (IAT) sensor -high input

By Ti (Contact Me)
Last Updated 2016-06-02
Mechanical Engineer

Table of Contents

1. What Does Code P0113 Mean?
2. What are the common causes of code P0113 ?
3. How do you troubleshoot code P0113 ?
4. Codes Related to P0113
5. Get Help with P0113

What Does Code P0113 Mean?

The P0113 occurs when the PCM reads a high voltage signal in the IAT circuit.

On most cars the IAT is located in the air intake box.  Look around the intake box for a cylindrical shaped object with a two wire lead.   If you don’t find two wires, the IAT may be integrated with the MAF sensor.  The IAT can sometimes be found on the intake manifold or plenum.

IAT Wiring Diagram

The electrical circuit for the IAT is shown below:

The IAT is calibrated and outputs a voltage proportional to the air temperature.  Higher temperatures cause the PCM to read higher voltages because the IAT’s internal resistance is reduced when heated.

See the IAT in depth article (P0112) for more background on the IAT sensor.

Note: Circuit High Input codes are mostly caused by defective alternators that develop excessive voltages, although there may be other causes as well, such as short circuits that “leak” current into a particular system from other, unrelated systems that work on higher voltages. Note that in the case of short circuits that leak power into a control circuit, there is likely to be other, seemingly unrelated trouble codes present along with the code(s) being investigated. Diagnosing a “high input” code will always involve a thorough testing of the charging system as a first step, followed by measures to isolate the system from all other possible sources of power during resistance, continuity, and reference voltage tests.

What are the common causes of code P0113 ?

The P0113 code often occurs when there is a break in the wiring to the IAT sensor.

How do you troubleshoot code P0113 ?

This is a simple circuit, just two wires running from the ECU to the IAT sensor. If you have access to a scan tool, you can use it to read temperatures directly, otherwise you can use a DVOM (digital volt-ohm meter), thermometer, and a short pin, such as a thin wire or paper clip. A resistance table for your specific year, make, and model, will be especially helpful. You can often find these online, or perhaps if you ask your local trusted automobile technician.

1. Sensor Check – With the key in the off position, disconnect the IAT sensor. With your DVOM set to Ohms Ω, measure the resistance across the terminals of the sensor.
   1. If you read an open circuit or short circuit (∞ Ω or 0.0 Ω), the sensor is at fault. Replace the sensor and you should be good to go.
   2. If you read resistance, check it against the temperature / resistance chart. If the engine is cold, then the IAT temperature / resistance should be fairly close to ambient temperature, which you can measure with a thermometer. If the resistance is correct at ambient temperature, you may still have a sensor problem. A sensor that reads properly at ambient temperature may go out of range at other temperatures. You can check for sensor problems by checking the resistance after you change its temperature, such as by putting it in a pot of boiling water or in the freezer.
2. Circuit Check – If the sensor itself appears to be properly responding to temperature changes, then you can proceed with circuit checks.
   1. With KOEO (key on, engine off), disconnect the IAT sensor, and check for voltage in the connector.
      1. One of the wires should read 5 V reference. If you have no 5 V reference, you may have an open circuit or an ECU fault.
      2. The other wire should read 0 V. If you can properly identify the signal wire, check for resistance to ground, which should read 0.0 Ω. An open circuit likely means you have a wiring problem. On the other hand, 0.0 Ω could still indicate a short to ground.
   2. If there is no 5 V reference voltage, there could be an open circuit between the ECU and the sensor, a short circuit to ground, or the ECU itself may be at fault. If there is no signal voltage on the other line, then you could have a defective sensor, open circuit, or short to ground.
      1. At the ECU, check for reference and signal voltage. If there is no 5 V reference, the ECU may be at fault. If there is low or no signal voltage, check for corrosion or an open circuit in the wires to the IAT sensor.
      2. Turn the key to the off position, disconnect the ECU connector, and check for resistance. If the resistance reading is the same as the sensor check, then the ECU may be at fault. If you measure 0.0 Ω or ∞ Ω, check for open or short circuit in the wiring to the IAT sensor.

• Disconnect the sensor and measure resistance again, it should now read as an open circuit, ∞ Ω. If you read any resistance at all, check for short circuits in the wiring to the IAT sensor.

1. Install a short wire, in the IAT sensor connector, and check for resistance in the circuit.
   1. The proper reading should be 0.0 Ω. Any reading over 1 Ω could indicate corrosion or an open circuit.
   2. Check for resistance to ground. Any reading under 1,000 kΩ could indicate a short to ground in one of the wires to the IAT sensor.
2. If you have access to a scan tool and live data, you can perform many of these checks simply by reading ECU IAT readings. With KOEO, read the temperature with the sensor connected, and then disconnected. If there is no change, you have a circuit problem. If there is a change, you have a sensor problem.

Codes Related to P0113

P0110
P0111
P0112
P0114

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