P0102 - Mass Air Flow Sensor Circuit Low
Mass Air Flow Sensor (MAF)
The mass air flow or MAF sensor measures the amount of air entering the engine. The engine computer (ECM) uses the mass air flow signal to calculate the amount of fuel injected (read more how the MAF sensor works below). The code P0102 is set when the signal from the mass air flow sensor is lower than expected. Often a car may exhibit some driveability symptoms, such as lack of power, surging, hesitation on acceleration, hard starting, pinging (detonation), or rough idle when started cold. Often the codes P0171 or P0174 could also be stored along with the code P0102, as the incorrect air flow signal can cause the engine to run lean. The codes P0171 and P0174 indicate a lean condition. Checking the freeze frame might help in the diagnostic process. The freeze frame is stored in the ECM along with the trouble code. The freeze frame contains some recorded parameters (e.g. vehicle speed, engine temperature, fuel trim) at the moment when the fault was detected. The freeze frame can also be accessed with a scan tool.
What could cause the code P0102
- faulty or contaminated mass airflow sensor
- debris blocking the air flow at the mass air flow sensor
- unmetered air leaking past the MAF sensor (vacuum leaks)
- PCV system vacuum leaks
- restricted or collapsed intake air duct
- dirty or restricted air filter
- restricted air screen before the air filter
- improper application of aftermarket components (e.g. cold intake, modified air filter, etc.)
- wrong air flow sensor installed
- electrical problem with the MAF sensor wiring, connector, power supply or ground.
- problem with ECM
- in some cases other issues with the fuel injection system like a clogged catalytic converter or a faulty manifold absolute pressure sensor (MAP) can also cause the code P0102.
In many GM vehicles the code P0102 is often caused by a faulty mass air flow sensor. The repair involves clearing the code and replacing the MAF sensor if no other problems found.
A Nissan technical service bulletin (TSB) for the trouble code P0102 in 2002 Nissan Maxima recommends removing debris from inside the air filter housing, replacing the airflow meter assembly and reprogramming the ECM. A Toyota TSB describes a problem with 2006 Toyota Tacoma, where loose terminals in the MAF sensor connector could cause the code P0102; the connector must be checked and repaired if needed. In some Volkswagen cars, the code P0102 is often caused by a faulty mass airflow sensor; the repair often involves replacing the mass air flow sensor and clearing the code if no other problems found.
What needs to be checked:
The air duct between the mass air flow sensor and the engine intake needs to be checked for cracks, tears, loose clamps or improper connection. The connector and the wiring at the mass air flow needs to be checked for loose terminals, corrosion or damage. The air filter element needs to be checked and replaced if dirty. Some cars (e.g. Volkswagen, Audi) have a screen inside the air duct before the air filter that might be called Snow Screen. This screen needs to be checked for blockage, as often leaves and other debris block the air flow. The mass air flow sensor needs to be checked for contamination or dirt blocking the sensor element. If the mass air flow sensor element is dirty, cleaning it may help temporarily; however, the element is very delicate and should be cleaned very carefully to avoid damage. The mass air flow reference voltage and ground must be checked at the sensor connector. The signal voltage or frequency needs to be checked at different engine RPMs and compared to the reference chart. The easiest way to check the mass air flow sensor is with a scan tool, reading the measured air flow at different RPMs. The long and short fuel trim readings are also need to be checked with a scan tool. Most of the time the solution for the code P0102 involves replacing the mass air flow sensor if no other problems found. An improper or poor quality part also can cause the code P0102, so it's better to use an OEM mass air flow sensor. Typically a new mass airflow sensor is priced from $70 to $350. Replacing the MAF sensor is easy and won't cost a lot at the repair shop. If the problem is fixed, the code P0102 will clear itself after driving.
How the mass airflow sensor works:
The mass air flow sensor is installed in the engine compartment in the intake air duct between the air filter and the engine intake manifold. The engine computer (ECM) uses the signal from the mass air flow sensor to calculate the proper amount of fuel to
Mass Air Flow Sensor (MAF)
inject into the engine. When the car is accelerated, more air passes through the air flow sensor. The computer immediately commands the fuel injection system to add more fuel. When the engine is idling, less air passes through the mass air flow sensor and the amount of injected fuel is reduced. In some cars, the MAF sensor produces the voltage signal; in others the frequency signal is used instead. The ECM interprets the voltage or frequency signal from the mass air flow sensor into the amount of intake air flow. If the frequency signal is used, the code P0102 might read Mass Air Flow (MAF) Sensor Circuit Low Frequency, however the meaning is the same:
the sensor air flow measurement is less than expected. In many cars the air flow sensor signal is used to determine automatic transmission shifting points. A problem with the airflow sensor could alter the shifting pattern of the automatic transmission.
Read more about mass air flow sensor »
A: The MAF sensor is the first thing to check, it could be just dirty; check the air filter too. If the sensor looks clean and the air filter is OK, the only way to test it is with a scan tool. The MAF readings at different RPMs need to be compared to the readings of a known good sensor. A bad MAF sensor was very common in many VW cars. A vacuum leak is another possibility - see if the intake air duct is connected properly and the vacuum hoses are not ripped. The code P0420 points to a failed catalytic converter, which is a separate problem.
A: If you don't have a scan tool to test the MAF sensor properly, replacing it could be a good first step. Bad MAF sensors were common on these cars. Use the OEM sensor. Even if it doesn't fixes the problem, at least you know that the MAF is good. Check the sensor connector and wiring too.