|Code||Fault Location||Probable Cause|
|P2199|| Intake air temperature (IAT) sensor 1/2- correlation |
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|Wiring, IAT sensor|
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What Does Code P2199 Mean?
OBD II fault code P2199 is a generic code that is defined as “Intake air temperature (IAT) sensor 1/2- correlation”, and is set when the PCM (Powertrain Control Module) receives input data from the Intake Air Temperature sensors that exceeds a redefined max/min difference between them, or, a reading from an IAT sensor that is implausible given the current operating conditions or ambient temperature. Put in another way, the readings (signal voltages) from both IAT sensors on applications that use multiple IAT sensors have to agree, or correlate with each other within a narrow margin. If this does not happen for whatever reason, the PCM will set code P2199 and possibly illuminate a warning light. Note that code P2199 only applies to applications that use multiple IAT sensors.
Since ambient temperature has a direct bearing on the density of air, some manufacturers use two IAT sensors to refine the amount of air required to maintain an ideal air/fuel mixture at all times. In practice, cold air is denser than hot air, which means that a smaller volume of air relative to any given volume of fuel is required to maintain a stoichiometric (14.7 parts of air to 1 part of fuel) air fuel/fuel mixture on gasoline engines. Conversely, when the ambient temperature is high and the air is less dense, a larger volume of air is required relative to any given volume of fuel to maintain a stoichiometric air/fuel mixture.
While most applications that have only one IAT sensor manage the air/fuel mixture reasonably well with the aid of an oxygen sensor, the PCM’s on applications that use two IAT sensors have more data available to them. By comparing the intake air temperature when it enters the air inlet tract with the intake air temperature closer to the throttle body, the PCM has more accurate data on the temperature that actually enters the engine, and it can therefore regulate the amount of fuel required to maintain a stoichiometric air/fuel mixture more precisely than is possible with only one IAT sensor.
The practical advantage of this is that since the air/fuel mixture is better regulated and controlled, the adaptations to the air/fuel mixture that the PCM makes from time to time are smaller and less frequent than would have been the case with only one IAT sensor, which in turn, translates into improved engine performance, increased fuel economy, and less harmful exhaust emissions.
The image below shows a typical location of one IAT sensor (circled in red) close to the air filter enclosure. Note though that the other IAT sensor may be located inside the throttle body, and may or may not be incorporated in to the MAF (Mass Airflow) sensor. Refer to the manual for the affected application to locate and identify both IAT sensors correctly.
What are the common causes of code P2199?
Some common causes of code P2199 could include the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
- Defective IAT sensors
- In some cases, oil contamination of an IAT sensors’ element can cause this code
- Failed or failing PCM. Note that this is a rare event, and the fault must be sought elsewhere before any controller is replaced
What are the symptoms of code P2199?
Some common symptoms of code P2199 could include the following-
- Stored trouble code, and possibly an illuminated warning light
- Fuel consumption may increase
- Some applications may exhibit a lean-running condition at cold start-up, while others may exhibit a rich running condition at cold start-up
NOTE: In many cases, there may be no discernible symptoms at all apart from a stored trouble code. Note also that this code very rarely causes driveability issues.
How do you troubleshoot code P2199?
NOTE: Apart from a good quality digital multimeter, a wiring diagram and a temperature-to-voltage chart for the application, an electric hair dryer will be helpful in diagnosing this code.
Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.
NOTE: If any other codes are present along with P2199, and especially codes relating to reference voltage circuits, resolve all codes preceding P2199 before attempting a repair of this code to avoid a misdiagnosis, wasted time, and the unnecessary replacement of parts and components.
Refer to the manual to locate and identify both IAT sensors, as well as their related wiring. Also determine the function and color-coding of each related wire to avoid testing the wrong circuit(s).
NOTE: Make absolutely sure to identify the signal return wire on each IAT sensor, particularly in cases where the IAT sensor is incorporated into the MAF sensor, to avoid testing the wrong sensor.
Once all parts and wiring are properly identified, perform a thorough visual inspection of all wiring and connectors. Look for damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors. Make repairs as required. When repairs are complete, clear all codes and operate the vehicle normally before rescanning the system to see if the code returns.
NOTE: Make a particular point of it to check if the connector of the IAT sensor located on or near the air filter enclosure is fully engaged, since it is very easy (even for professional mechanics) to forget to reconnect this connector after replacing the air filter, or when this connecter was disconnected during other types of routine servicing or maintenance.
If no visible damage is found, prepare to perform reference voltage, resistance, ground, and continuity checks on all wiring, but be sure to disconnect both sensors from the PCM to prevent damage to the controller.
Compare all obtained readings with the values stated in the manual, and repair or replace wiring as required to ensure that all electrical values fall within the manufacturers’ specified ranges. When repairs are complete, clear all codes and operate the vehicle normally before rescanning the system to see if the code returns.
NOTE: Pay particular attention to the reference voltage circuits during this step, since the IAT sensors use this voltage to general a signal voltage. If a major deviation from specified values is found in this circuit, but the circuits’ resistance check out, consult the manual for details on the correct procedure to check if the PCM is delivering the correct reference voltage. Bear in mind however that if the PCM does not deliver the correct reference voltage (usually 5 volts), other sensors may be affected as well since several sensors often share one reference voltage circuit.
If the code persists, but the PCM delivers the correct reference voltage, remove the IAT sensors and attach the probes of the multimeter to one sensor’s connector in such a way that proper contact is ensured. Insert the red probe into the connector from the back on the signal return wire, and the ground the black probe securely.
Use the hair dryer to GENTLY heat the sensor. As the sensor element heats up, the signal voltage should change in a predictable manner; however, without knowing exactly how hot the air is that passes over the element, it is impossible to tell whether the sensor is reacting correctly, or by the correct amount. If a laser or infrared-based thermometer is available, take a reading of the air temperature that passes over the sensor, and compare this value with the manufacturers’ temperature to voltage chart. Replace the sensor if the resulting signal voltage does not agree with specifications.
Repeat Step 5 with the other sensor, and compare the results with those obtained during testing of the first sensor. However, if the second sensor is incorporated into the MAF sensor on an application that is known to have a high rate of oil consumption (VW, BMW, AUDI, or Mercedes) clean both the MAF sensor and IAT sensor elements with an approved cleaner, and repeat the test. If the correlation error persists, replace the combined MAF/IAT sensor with an OEM part to ensure proper operation.
NOTE: While it is not always strictly necessary to replace both IAT sensors when one fails, it is almost always preferable to do so, since the accuracy of one or both sensors may be affected after several years’ use. In practice, this means that the correlation error may persist when one sensor is new and the other is not, and especially so if the sensors are not of the same brand.
When repairs are complete, clear all codes and operate the vehicle normally before rescanning the system to see if the code returns.
If the code persists, or returns soon after, it is likely as the result of an intermittent fault. Faults of this type can sometimes be extremely challenging and time consuming to find and repair, and in some cases, it may be necessary to allow the fault to worsen before an accurate diagnosis and definitive repair can be made.
Codes Related to P2199
There are no known codes that are directly related to P2199 – “Intake air temperature (IAT) sensor 1/2- correlation”.
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