What does it 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.