Engine Troubleshoot

P0102 Mass Air Flow MAF Circuit Low

faulty MAF

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What Does Engine Code P0102 Mean?

  • P0102 Technical Definition: Mass Air Flow MAF Circuit Low
  • P0102 Meaning: Mass Air Flow Sensor is not working properly
  • Most common cause: Air (vacuum) leak, dirty or failing mass air flow sensor
  • Risks for the engine/driver: Low You should get the car checked out as soon as possible
  • Emissions severity: HIGH. The car won’t pass emissions testing
  • Estimated repair time: 1 day
  • Estimated repair cost: $200+

The engine code P0102 is stored in memory when the Electronic Control Unit (ECU) detects that the Mass Air Flow (MAF) sensor readings are outside its expected calculated value.

The Mass Air Flow Sensor is one of the main electronic components of the fuel delivery system. Its job is, in real time to measure, the mass of air entering the engine. This information is used by the ECU to determine the amount of fuel needed to achieve the stoichiometric ratio consisting of 14.7 parts of air per each part of fuel.

This calculation is then adjusted after analyzing the data from the rest of sensors, especially the oxygen sensor feedback that is used as a key input for the corrections of the next computing cycle.

In other words,  without the MAF data, the ECU would be nearly blind regarding air flow making it very difficult to achieve proper fuel delivery. On modern vehicles, a “reference” MAF value is calculated by the ECU using the information from the rest of the engine sensors. This calculated value is compared to the actual MAF output in order to check the sensor performance. 

The P0102 code is set when the ECU detects a low circuit voltage in the MAF signal that do not correspond to its expected value.

7 Common Symptoms When Code P0102 is Present?

The most common symptoms of data trouble code P0102 are:

  1. Check Engine Light (CEL).
  2. Difficulty during engine start.
  3. Poor fuel economy.
  4. Rough idle.
  5. Engine hesitation during acceleration.
  6. Engine hesitation under load.
  7. Gas smell from the exhaust pipe.

Possible Causes For Error Code P0102

The most common causes of data trouble code P0102 are:

  1. Damaged MAF sensor wiring
  2. Damaged MAF sensor connector (loosely, corroded, disconnected or bent pins)
  3. Dirty or clogged MAF sensor
  4. Bad MAF sensor
  5. Intake manifold air leaks.
  6. Dirty, clogged or restricted air filter
  7. Faulty fuel pump relay
  8. Possible fuel pump faults
  9. MAP sensor fault
  10. Damaged wiring or blown fuse

How To Diagnose The Engine Code P0102

For the purpose of this article, it’s assumed that you have a basic knowledge of safety precautions while working on your vehicle.

Always refer to the appropriate OEM literature when possible. Original manufacturer diagnostic procedures should always have precedence over a generic workflow.

That said, let’s start the diagnostic process!

1. Preliminary steps

To discard a possible intermittent DTC condition, you’ll need to clear the ECU memory and complete a driving cycle. A damaged or dirty Mass Air Flow Filter may also throw up a P0101 error code during the diagnostic process. Other errors may show up too if other components are at fault. For example a faulty MAP sensor will give a P0106 error.

  • Read data trouble codes and take note of them.
  • Clear data trouble codes memory.
  • Perform a driving cycle (at least 5-10 minutes).

In case the Check Engine Light stays off then you may have an intermittent problem. If the light lit during your driving cycle then continue with the diagnostic process.

2. Visual Inspection

> Vacuum hoses: perform a meticulous visual inspection of all vacuum lines, including MAP sensor, PCV, brakes vacuum booster, fuel pressure regulator, etc. Also, check the air intake hose looking for any sign of deterioration or leak.

> MAF condition: to inspect the MAF condition you will need to remove it from the vehicle first. Please refer to our MAF article for detailed instructions on how to diagnose in detail and clean this important sensor.

> Air Filter inspection: a clogged air filter could decrease the Turbocharger/Supercharger boost pressure significantly. Check the air filter condition and replace if necessary. 

Fix any wiring problem before continuing.

3. Electrical Tests

> MAF electrical tests: due to this sensor importance you should perform a comprehensive electrical test including continuity, reference voltage, ground, and supply voltage. Refer to our MAF article for detailed instructions about this procedure.

4. Scan Tool Tests

> Mass Air Flow Sensor live test: using an automotive diagnostic scanner you can perform a MAF “live test”. First, enter in KOEO mode and lock the MAF sensor related data on the display.

Depending on your vehicle and scan tool maker you may have several items to check. Focus on the calculated MAF output, often expressed in grams per second. You could also lock on screen the MAF output voltage if you can’t find its calculated value.

Once you are ready to start the engine to enter KOER mode. If your scan tool has a graphing ability turn it on. Graph engine RPM and MAF output at the same time. Gently accelerate and decelerate the engine. The resulting lines should be similar, increasing and decreasing simultaneously. The greater the difference between them the greater the probability that you have a bad mass air flow sensor.

How To Repair Engine Error Code P0102

Depending on the diagnostics results you may need to do the following:

  • Repairing the MAF sensor wiring and/or connectors.
  • Cleaning the MAF sensor
  • Replacing the MAF sensor
  • Replacing the air filter
  • Repairing vacuum leaks