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Diagnosing Check Engine Code P0102

Low Air Flow Through Your Engine Air Filter

So your check engine light is on again, huh? Good thing you bought that OBD2 scanner after reading our last blog post on Check Engine Code P0101. If you didn’t read that blog yet, no worries! Follow the links to the blog post and the OBD2 check engine light scanner and become the master of your own car repairs. Now let’s get down to the cause of your new check engine code P0102.

Check Engine Code P0102: Mass Air Flow (MAF) Circuit Low

Check engine code P0102 triggers when the MAF sensor or mass air flow sensor detects a low volume of air coming through your air filter. When researching this code you will find that the definition is Mass Air Flow (MAF) Circuit Low and there are a couple of things that can cause this. Below we will cover the symptoms to look for, the possible causes, and maybe even a fix or two.

What is a P0102 check engine code?

Your mass air flow sensor is installed after your air filter and inside your air intake tube. The location is usually easy to determine with a simple surface inspection because there is a power supply that plugs into the sensor on the outside of the intake tube. This sensor measures the volume and density of the air passing into your intake system and through the engine. Error code P0102 indicates that the air traveling through your air filter is insufficient for a proper fuel-to-air ratio. In other words, your car will be “running rich.”

Not to get too technical but the sensors base the airflow on a calculation for volume and density. If the measure of airflow drops below the intended minimum volume or density requirements for either calculation, it triggers the check engine code P0102.

Symptoms of Low Air Flow Through Your Engine Air Filter

  1. Your first symptom is usually the check engine light, which by itself just tells you that something is wrong with your car or truck. Without an OBD2 reader to scan and decipher the code, you get stuck having to let someone else tell you what’s wrong.
  2. Look for a rough idle or a rough running engine. If your car or truck is having trouble breathing, it’s going to have a cough and a wheeze. It’s going to sound sick. Your engine may sputter, have an erratic idle (going up and down), and it may hesitate as you try to accelerate.
  3. Frequent engine stalling is another common symptom of your engine not getting oxygen. Nothing lives without oxygen.
  4. Black smoke from your exhaust – This happens when your car is “running rich”. In other words, your vehicle will be burning more gas than it’s supposed to in the combustion process causing black smoke and maybe even a rich gas odor in the cab and behind your car.

What causes your car to have low air flow through the air filter?

  1. Dirty or bad MAF sensor – Ok, so this doesn’t actually cause low air flow through the filter or your engine but it can still cause a P0102 check engine code. ALWAYS check the sensor first to make sure you don’t spend money on other fixes.
  2. Dirty Air Filter – Simply check your air filter for an obstruction. Is it dirty or clogged?
  3. Air intake leaks or damage – Are there gaps where your intake tubes meet? Inspect flex tubes and rubber seals or corners in your air intake system. Any tube that’s designed to flex or move to make the installation easier is more likely to break in those flexible areas. Convenience always comes with consequences.
  4. Bad MAF connector – Test the voltage to your MAF sensor. If you have faulty wiring, a bad connection, or a bad mass air flow sensor you may have to replace the wiring, the connector, or the whole MAF sensor.

You do need to repair this issue quickly. If the problem is a bad MAF sensor then it will hurt the vehicle or its engine but the check engine will stay on and you won’t know if there is a problem somewhere else in the vehicle until you have cleared the mass air flow error code.

How to fix low air flow errors

  1. If the issue is simply a bad or dirty mass air flow sensor, get yourself some MAF sensor cleaner. Yes, there is such a thing and it’s important to get the right stuff. Mass air flow sensors have very sensitive wiring. Spray the sensor in 5-second intervals, waiting 10-15 seconds between sprays. 2 to 3 sprays are usually enough. Let it air dry and DO NOT WIPE the sensor because you will break the wires doing so.
  2. A dirty air filter is an easy diagnosis. Pull it out of the vehicle, checking to see if was seated properly. Hold it up to a light source and look for light shining through the filter. If you can see light through 75% or better of the filter it’s likely fine but use your best judgment on whether to replace it. If you have one of the fancy lifetime air filters that you can just keep rinsing off, then give it a good rinse and let it air dry until it’s fully dry and ready to reinstall. Make sure it’s seated properly and seal it back up.
  3. Inspect the whole air intake system for intake system air or vacuum leaks. Leaks will reduce air flow through the intake system resulting in your engine running rich. Replace any compromised part of the air intake systems, and be sure to check any flexible parts, all connections, seams, and rubber seals if present.
  4. A bad mass air flow sensor connector or wiring issue can be a little more difficult to diagnose but as long as you have a multimeter and a little electrical know-how, you can get this task done. The voltage reading of your MAF sensor should be between 0.60 to 0.80 volts when your car is idling. This does depend on your MAF sensor.
    1. If your multimeter reads somewhere around 12v +/- you have your probe on the power wire, not the signal wire. Adjust your probe and read again.
    2. If your reading is below 0.60 or above 0.80 and you are not on the power source, your connector is likely bad or shorted. Rewire a new connector and plug it in.
    3. If your sensor is clean and the connector is reading between 0.60v - 0.80v +/- then the issue may be that your MAF sensor is bad. If you have tested and inspected everything else, try replacing the mass air flow sensor. THIS SHOULD ALWAYS BE THE LAST RESORT.

    What's Next?

    Now that you have restored your air intake system to its operational configuration, use your OBD2 to reset your check engine code. Almost all OBD2 scanners have this ability. The instructions to do so vary so if you’re not sure how to do it please refer to the OBD2 owner’s manual.

    It’s important to note that because of how your air intake system operates, any clogs, obstructions, damage, leaks, bad sensors, etc may result in several different but related codes. Any of the error codes P0100, P0101, P0103 and P0104 can be the result of the issues described here. The diagnostic process as well as the repairs are often very similar between them.

    Just a couple of notes: When unplugging anything electrical in your car or truck, be as gentle as possible because the plastic on these plugs is rigid and gets very brittle over time. If you break a tab, you will need to replace the plug to ensure a proper tight connection.

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