Trouble codes are a set of numbers and letters that indicate the nature and location of a potential issue within your vehicle. When these codes are stored, the vehicle’s computer illuminates the check engine light to alert you that an error is present.
The P0127 code is a trouble code indicating a possible problem with the intake air temperature sensor or its circuit. What does this code mean and what signs should you look out for? Find out with this brief guide.
What Does the P0127 Code Mean?
Diagnostic trouble code (DTC) P0127 stands for “Intake Air Temperature Too High.” This code is stored when the powertrain control module determines that the voltage levels from the intake air temperature sensor are higher than the maximum limit. This code may also set if the PCM perceives a potential error with the intake air temperature sensor or its circuit.
Note: The definition of code P0127 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.
The intake air temperature sensor measures the temperature of the air that goes into the engine. The PCM uses the input from this sensor, as well as from the mass air flow (MAF) sensor, to calculate fuel delivery and ignition timing. The data is also important in maintaining engine performance and maximizing fuel efficiency.
The intake air temperature sensor is a two-wire thermistor sensor. This means that the sensor’s resistance changes depending on the temperature of the air flowing through its cold wire element. More air flowing across the cold wire element means it provides a lower degree of temperature and resistance.
These variations in the intake air temperature sensor’s resistance create voltage fluctuations in the input circuit. These fluctuations are interpreted by the PCM as variations in the intake air temperature.
Since the intake air temperature sensor’s input is crucial to the PCM’s calculation of fuel delivery strategy, this code must be addressed immediately.
What Are the Possible Causes of the P0127 Code?
Trouble codes can only indicate the nature and location of a potential issue, not the exact root cause. This is why many trouble codes have multiple possible triggers. Like many diagnostic trouble codes, the P0127 code has a number of possible causes, some of which are listed below:
- Intake air temperature sensor failure
- Wiring issues such as open or shorted intake air temperature sensor wiring and/or connectors
- Faulty mass air flow (MAF) sensor (sometimes the IAT is integrated into the MAF)
- Defective intake air inlet pipe
- PCM failure
What Are the Common Symptoms of the P0127 Code?
When the vehicle’s computer system detects a potential issue, it stores the information as a diagnostic trouble code and sends a signal to illuminate the check engine light. In many cases, it may be the only sign of an existing error. For other trouble codes such as the P0127, other symptoms may also be present. Listed below are some of the indicators of a P0127 code:
- Malfunction indicator lamp (MIL) or check engine light on
- Poor fuel efficiency
- Decreased engine performance
- Other drivability codes may also be stored
How to Diagnose the P0127 Code
Proper diagnosis of a diagnostic trouble code requires accuracy and precision. Trouble codes have multiple possible causes, so it may take some effort and time to narrow down the root cause of the issue. In addition, misdiagnosis is also a possibility, which can cost you even more in future repairs.
In order to get an accurate diagnosis, you will need reliable sources of repair information. The best resources you can use are vehicle-specific repair manuals and databases, which contain accurate troubleshooting instructions as well as helpful diagrams and illustrations.
Technical service bulletins (TSBs), which can often be found through a repair database, may also help you get more information about a trouble code. TSBs are especially helpful if your vehicle’s manufacturer released one that’s applicable to the model you own. Other resources you can use and access online include how-to videos, blogs, and digital magazines.
How to Fix the P0127 Code
Fixing trouble codes is difficult enough because you have to accurately diagnose the problem first. That in itself is challenging already because a trouble code can have multiple possible causes.
Another factor that may complicate your troubleshooting process is the fact that vehicles aren’t built the same. Different manufacturers will have different terminologies, components, and repair instructions for their vehicles. For example, the setting conditions for a P0127 on a Volvo vehicle are different from those of a P0127 on a Nissan vehicle.
Because vehicles are manufactured differently, you definitely need a reliable and vehicle-specific repair manual to help you address the issue at hand. However, doing trouble code repairs on your vehicle without the right technical know-how may be dangerous and potentially damaging to your vehicle. That’s why if in doubt, have a certified professional do the repairs for you.