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The onboard diagnostic (OBD) code P0101 refers specifically to a Mass or Volume Airflow Circuit Range/Performance Problem. In a vehicle, the mass airflow (MAF) sensor measures the amount of air going into the engine through the intake. The powertrain control module (PCM) then uses that information to calculate how much fuel should be delivered to the engine.
The P0101 code indicates that there is a problem with the mass airflow sensor or its circuit. In this instance, the PCM will detect that the frequency signal given off by the MAF is not within the pre-programmed range of the calculated MAF value that it’s supposed to be, which is for more than 4 seconds.
- Check engine light illuminated
- Engine stalls soon after starting
- Engine drags or hesitates when idle or under load
- Engine hesitates and jerks during acceleration
- Engine seems to “hiccup”
- Engine idles either lean (too little fuel) or rich (too much fuel)
- A mass airflow (MAF) sensor that is either dirty, blocked, or faulty.
- Intake boot is disconnected or damaged (cracks or rips)
- Vacuum Leaks
- Air filter that is clogged or improperly installed
- The element of the MAF sensor is clogged or contaminated.
- Catalytic converter is clogged or exhaust is restricted
- Electrical problems with the MAF sensor or its wiring
What To Check
When you first notice that the check engine light is on, confirm the code that it’s returning by using an OBD-II scanner (to do this yourself, go to any auto parts store and they will do it for you for free). Once the P0101 code is confirmed, you can begin to check specific parts of the engine that are contributing to the problem.
If the intake manifold has been cleaned recently and chemical solvents were used to clean it, this can potentially damage the mass air flow sensor. Also, check for foreign objects (like leaves) that could have clogged up the airflow sensor measuring element.
In addition, if the air filter was recently replaced, make sure it was properly installed. This can affect the operation of the airflow sensor as well.
Check the wiring harness for the MAF sensor. Ensure that it is not incorrectly routed too close to these parts:
- the secondary ignition wires or coils
- any solenoids
- any relays or motors
Check the intake boot for any cracks or rips – if the intake boot is damaged, the air that is supposed to go to the engine is probably leaking out of the existing cracks and rips. In addition, inspect for other sources of vacuum leaks – including intake gaskets and the PCV valve.
An automotive technician can also test the mass air flow using a scan tool that will measure air intake at different rpm levels and then be compared to the specifications for the make and model of the vehicle.
Finally, the catalytic converter should also be checked to see if it is clogged – this can happen on some vehicles and lead to the P0101 code being produced. A mechanic can diagnose this by checking the exhaust back pressure.
How to Fix It
The simplest solution is to reset the computer and see if the code comes back. If it doesn’t, test the engine performance for symptoms and see if they return. If they do, then proceed with further diagnosing the problem. Additional repair tips will depend on the particular make and model of your vehicle.
If the air filter has been improperly installed, then reinstall it properly. Also, check to make sure the air filter isn’t overly clogged or dirty and if it is, then remove it and replace it.
If the wiring harness was found to be installed to close to the above-mentioned components, then it will need to be rerouted.
Replace the mass airflow sensor and recheck engine performance. If it improves, it means the sensor was faulty. Also, check to see that the airflow sensor measuring element isn’t clogged. If it is, remove the debris, reset the engine computer, and test the engine’s performance again.
If the intake boot is ripped or cracked, then it needs to be replaced.
Fortunately, P0101 is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.