Fault code P0127 – intake air temperature too high

Fault code P0127 is called “Intake Air Temperature (IAT) Too High” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0127

Fault code P0127 is a generic fault code defined as too high intake air temperature. It is set when the PCM control module detects an abnormally high voltage signal from the IAT sensor.

Fault code P0127 – intake air temperature too high

In a fully functional system, the PCM uses inputs from the Mass Air Flow (MAF) sensor and the IAT sensor to calculate the fuel delivery strategy. The MAF sensor monitors the total volume of air entering the engine, and the IAT sensor monitors the actual intake air temperature.

Intake air temperature plays an important role in fuel management because the hotter the intake air, the less dense it becomes. This means that in order to maintain the correct air/fuel mixture ratio (14.7: 1), the PCM must constantly adapt the amount of fuel delivered to the injectors.

In most systems, the IAT sensor is a simple thermistor whose resistance changes as the temperature of the air passing through it changes. The PCM supplies the sensor with a 5 volt reference voltage, the voltage of which varies in direct correlation to the change in resistance of the sensing element.

The resistance changes are sent to the PCM through a special signal wire, and the PCM perceives them as changes in the intake air temperature.

The intake air temperature sensor measures the temperature of the air entering the engine. The Power Control Module (PCM) uses this information to determine how much fuel to use for normal engine operation. When the PCM detects a problem with this sensor or sensor circuit, it sets code P0127.

Symptoms of vehicle malfunctions

The main signal that an error P0127 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be memorized as a fault).
  2. Other related fault codes may also be present.
  3. The vehicle engine may run erratically at idle.
  4. Engine jerking, and attempts to stall under load or acceleration.
  5. Reduced engine power output.
  6. Increased fuel consumption.

The PCM uses the IAT sensor signal to calculate a fuel strategy, so code P0127 should be considered serious. In addition to increased fuel consumption, this fault affects driving safety.

Factors that can cause this error code

The error code P0127 can mean that one or more of the following problems have occurred:

  • The intake air temperature sensor (IAT) is defective.
  • Intake air temperature sensor wiring harness is broken or shorted.
  • IAT sensor connector is open or damaged.
  • Mass air flow sensor (MAF) is defective.
  • Clogged air filter.
  • Faulty intake air intake manifold.
  • Sometimes faulty PCM is the cause.

How to fix or reset OBD-2 code P0127

Some suggested steps for troubleshooting and fix the error code P0127:

  1. Check IAT sensor wiring and connectors for malfunction. Repair or repair damaged components.
  2. Verify that the intake air temperature sensor (IAT) is good.
  3. Check the mass air flow sensor (MAF).
  4. Inspect the air filter; if it is clogged, replace it.
  5. If there are no problems, the PCM may be defective.

Diagnose and repair of problems

Before starting to diagnose error P0127, write down all available fault codes as well as all available freeze frame data. This information may be useful if a recurring fault is later diagnosed.

Conduct a thorough visual inspection of the sensor connector and wiring. Look for damaged, burned, shorted, disconnected, or corroded wiring and connectors. If necessary, repair or replace damaged areas.

If no visible damage is found, perform reference voltage, resistance, ground, and continuity checks as instructed in the manual. Compare all readings with the values given in the manual; if any abnormalities are found, repair or replace the wiring.

If all electrical parameters in the circuit have been checked, remove the IAT sensor from the intake line, but leave the connector plugged in. Use a hair dryer to gently heat the sensor while observing its readings on the scan tool.

Depending on operating conditions, the voltage will change up or down as the sensor heats up.

Use an infrared thermometer to read the temperature sensor and compare it to the temperature vs. voltage table. Replace the IAT sensor with an original sensor if the temperature readings do not match the manufacturer’s specifications.

Clear all the codes after the repair work is completed and test drive to see if the code returns. In some cases, if code P0127 returns, there is most likely an intermittent fault in the wiring or the sensor itself.

On which vehicles does this problem occur most frequently

Fault code P0127 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chrysler
  • Dodge
  • Ford
  • Hyundai
  • Jeep
  • Mazda
  • Nissan (Frontier, Xterra)
  • Skoda

Fault code P0127 can sometimes be found with other errors. The most common are the following: P0110, P0111, P0112, P0113, P0114.

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