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P1101 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Mass airflow sensor out of self-test range


The OBD2 error code P1101 is the trouble code that is triggered when the Powertrain Control Module (PCM) encounters difficulty in conducting the self-test on the Mass Air Flow Sensor (MAF). 

The Mass Air Flow Sensor (MAF) is designed to measure the amount of airflow in the engine when the engine is running. 

For a typical automobile, during the key ON engine OFF, the stipulated airflow voltage expected should be higher than 0.27 volt, subsequently, during the key ON engine Running, the airflow voltage is expected to be between the ranges of 0.46 volt to 2.44 volts. 

However, if during the self-test run called Key On Engine Running (KOER) test, the Powertrain Control Module (PCM) detects a voltage lower than 0.27 volt during the key ON engine OFF, or below 0.46 volt or above 2.44 volt during the key ON engine Running then the DTC code P1101 is triggered.


There are a number of conditions that could cause your vehicle to give you the P1101 code; some of the most common causes are;

  • Faulty or defective electrical connection in the MAF sensor
  • Disconnected, damaged, or corroded wiring in the MAF sensor
  • Leaks downstream the MAF sensor 
  • Contamination of MAF sensor elements, such as oil contamination
  • Faulty or defected MAF sensor
  • Faulty PCM (this is the rarest cause of P1101 and it should be checked as the last resort if the error persists after fixing the other possible causes)


As with the cases of other DTC codes, P1101 has a number of symptoms to indicate its effect, most of which are related to the drivability issues. Here are the common symptoms of P1101

  • Illumination of the check engine light or the “service engine soon” light
  • Delayed pickup time
  • The engine runs below the average performance
  • High rate of fuel consumption
  • Rough idling


The diagnosis of P1101 as well as other DTC codes should be done by experts, such as a certified mechanic, however, if you decide to do this yourself, this article is written in the most simplified manner to guide you on a step-by-step basis. Before diving further, diagnosing P1101 requires advanced scan tools capable of reading and interpreting factory sensor readings and codes, such as the OBD-II scanner, as well as the digital volt/ohm meter (DVOM). However, these tools require trained personnel to read and interpret the readings. With these tools in hand, the following are the necessary steps to take for a proper and effective diagnostic process:

  • Conduct thorough inspection on the connections and wirings within the MAF sensor and other components associated with the MAF system;
  • After that, inspect the air filter for possible blockage and ensure there is no disturbance or hindrance of the airflow;
  • If after checking the MAF system there is a  need for repair or replacement of parts, the faulty part should be fixed as appropriate;
  • Then clear the code and test the system to check if the error code has been cleared successfully or not;
  • If the error persists after the steps above, then a clearer analysis on the error is needed and this can be gotten from the freeze frame data;
  • Go ahead to download any freeze frame data on the PCM with all the stored codes inclusive;
  • With great care, remove the MAF sensor to check for dirt accumulation and clear if any;
  • Having done that, conduct a smoke test, the aim of this is to detect any leaks downstream the MAF system;
  • Fix any leak that is detected during the smoke test conducted in the step above;
  • On the other hand, if no leak is detected or the error persists after the leak has been fixed, proceed to test the MAF sensor for reference voltage and ground signal;
  • If the step above fails, disconnect the PCM (Powertrain Control Module) and all other related modules;
  • Then inspect and ensure continuity of the MAF sensor and all related circuits with the battery ground;
  • Additionally, ensure the continuity between the MAF sensor and the PCM, as well as all other control modules;
  • Lastly, clear the P1101 code and conduct another test on the system to check if the code returns.

Common Mistakes

When dealing with the P1101, most mechanics easily opt for replacement of the MAF sensor when the problem can be solved by simply cleaning the MAF sensor. Therefore, before resorting to the replacement of the MAF sensor as your last option, ensure to check if cleaning of the MAF sensor can solve the problem. Another common error is the failure to check for possible leaks in the vacuum, this can equally lead to the persistence of the P1101 code.

How Serious Is P1101?

Although the P1101 would not prevent your car from running, however, there are a number of ways it would affect the performance of the car, for instance, theidleness which may occur at the most awkward moment, or the increased fuel consumption. These and many more would make the driver want to seek immediate remedy to the error. More so, prolonged use of a car with the P1101 error could lead to further damages to the vehicle’s engine. Therefore, while it is possible to use your car with the P1101 unrepaired, it is most recommended that you fix the error as soon as possible.

What Repair Can Fix P1101?

Here are the repair practices that can be carried out on your car to successfully clearthe P1101 trouble code;

  • The damaged or faulty parts of the MAF sensor should be repaired or replaced as applicable;
  • Tighten the loose wiring, connectors, or components within the MAF system;
  • If the P1101 is caused by dirt accumulation in the MAF sensor, the MAF sensor should be cleaned or replaced if the error persists after cleaning;
  • When cleaning the MAF sensor, the specialized cleaner should be used and it must be allowed to dry before it is being replaced;
  • Repair any leaks detected within the vacuum system;
  • Finally, if the PCM or any other control modules test as “bad”, then consider replacing them.


In conclusion, diagnosing or repairing the P1101 trouble code should not be done by novices as improper diagnosis and repair could lead to several complications in the car, therefore, if you encounter the P1101 endeavor to get a trained mechanic to attend to your car. However, should you decide to conduct the diagnostic test by yourself, we strongly advise you do so with proper care to avoid cases of “had I known”.

P1101 Code – What Does It Mean & How To Fix It