Home OBD Scanners P0101 code – Causes, information & Fix

P0101 code – Causes, information & Fix


 The error code P0101 indicates a problem in the vehicle’s mass airflow circuit and performance. In this article, we are going to look at the causes for this problem, the diagnosis and how to fix it.

Error code P0101 shows that there is a problem in the vehicles mass air flow sensor. The mass air flow sensor found in the engine regulates the amount of air entering the engine at a time.

It is a key component of the vehicle’s fuel injection system. The mass airflow sensor is located between the engine intake manifold and the air filter. In cars released recently, within the past five years, the mass airflow has an inbuilt air intake temperature sensor that enhances its efficiency.

The mass airflow sensor monitors the amount of air entering the engine at a given time. This information is then taken to the car’s onboard computer system where it helps adjusts the fuel injectors and timing settings. This is why the sensors have an electrical connector.

A hot wire found in the mass airflow sensors is used to detect the flow of air. It does this by measuring resistance as different amounts of air pass over it. Over time and mileage, the mass airflow sensor becomes inaccurate and must be cleaned for it to work how it is supposed to.

Symptoms of error code P0101

When the mass airflow sensor goes bad, wrong information will be sent to the onboard computer meaning the fuel injection process will be affected.

When this happens, the vehicle will show some signs of damage. The following symptoms should help you confirm the P0101 error code.

Rough idling

When the mass airflow sensor is affected, the engine control unit (the vehicle’s internal onboard computer system) will not know the amount of fuel to inject into the engine cylinders. When the wrong amount of fuel is injected into the cylinders, the car will start vibrating when making stops or slowing down.

These vibrations are what are referred to as rough idling. When the car rough idles, the RPM on the dash fluctuates at idle. And when you see this, you can now start worrying about a damaged mass airflow sensor

The engine stalls

If you keep experiencing engine stalling, there could be a high chance your mass airflow sensors are bad. You may start the car just fine in the morning but later on, the car stalls out of the blue.

This means that the airflow sensor circuit is damaged and indicates a P0101 error code. In serious cases, the car may fail to start at all. If you experienced rough idling together with stalling, this just confirms that your vehicle’s mass airflow sensor is damaged.

Causes of error code P0101

The error code P0101 is easy to diagnose. It indicates a problem in the mass airflow sensor circuit which basically means the sensors have gone bad. The following are the most common causes of this error code.

Dirty or faulty mass airflow sensor

Dirty airflow sensor cause the error code P0101. This is because when the sensors are blocked by dirt and debris, they send the wrong information to the engine control unit regarding the amount of air entering the engine.

Cleaning the sensors at least once every six months is recommended. A faulty sensor also sends the wrong information to the engine control unit causing the same error code.

Clogged air filter

When driving, a lot of dust and particles in the air and in the road are trapped in the air filter. When you go too long without replacing this filter, a lot of debris accumulated and affects the amount of air entering the mass airflow system.

This will reduce the amount of air entering the mass airflow system. Wrong information is sent to the ECU and a P0101 error code is found.

Leaks in the air intake system

When there are leaks in the vehicle’s air intake system, the amount of air entering the mass airflow sensors is significantly reduced.

This will cause the sensors to send the wrong information to the onboard computer regarding the volume of air needed in the engine cylinder. The computer then calculates wrong air and fuel ratios that indicate a P0101 error code.

How to test the P0101 error code

To diagnose or test this error code, you need an OBD II scanner and a screwdriver. Scan the onboard computer for other error codes related to the P0101 which include P0100-P0104. If you find any of these error codes, treat them first.

You should the read the real time readings of the oxygen sensors to check their operations. After doing this, check the air filter and ensure it is properly installed. Check whether it is clean and if not, clean it. Remove the air intake snorkel and visually inspect it for damage.

Check the wiring and ensure there are no broken and loose wires. Replace the faulty snorkel. After this, you should inspect the air intake system for leaks. Do this by running your fingers slowly against the hoses to feel cracks and weak spots.

Check their connection and ensure they are tightly connected. The final step involves doing a back pressure test to check for any clogging in the catalytic converter. Clean the clogging using catalytic converter cleaner.

How to fix the P0101 error code

You can fix this error code at the comfort of your home garage. Once you finish the diagnosis, the error code should be gone. However, if the error code persists, take the following steps to fix the problem.

  1. Replace the faulty wires found in the diagnosis part.
  2. Clean the mass air flow sensor. It is important to remember that the mass airflow sensor is a sensitive part and should only be cleaned with the cleaner specifically designed for this purpose. Spray the sensors with cleaner for 3 seconds then wait 10 seconds to spray again. After this leave it to dry as you need nit wipe it off
  3. Clear the error codes and test drive the car and check whether the error code comes back. If it is still there, replace the mass airflow sensor. Always remember to use the right replacement as an incompatiblesensor will lead to further damage which will be more expensive to fix.
  4. For Volkswagen vehicles, there is a mesh in the air intake system. Inspect this mesh for damage or accumulated dirt. Clean the mesh or replace it depending on the problem.
  5. Finally, inspect the catalytic converter. Clean it first then retest for the error code. If the error code persists, replace the catalytic converter.


The P0101 error code is as easy to detect and diagnose as it is to fix. When you do find this error code, get the problem fixed immediately as engine problems can be quite expensive if left to grow into bigger problems.

Regular vehicle maintenance is recommended to prevent this error code. Regularly check the air filters and replace it when necessary. This will go a long way in preventing the mass airflow sensors from damaging.

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Steven Reilly is a qualified mechanic and his passion for cars goes beyond just the technical aspects. He is also an amateur racer and all round car enthusiast. When he is not driving them, he can often be found in his garage under the hood of a rare model. Steven Reilly has lost track of the number of hours he has spent setting up his fine collection of rebuilt models. He believes that cars can provide a constructive and fun opportunity to teach the youth important life skills. In line with this, he is developing a community outreach program, potentially dubbed ‘Cars for change'.



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