Rick's Free Auto Repair Advice

P0101 code — What it means and how to fix it

Learn what a P0101 code means, the most common causes and fixes

A P0101 code is defined as Mass Airflow (MAF) Circuit Range/Performance Problem.  relates to a problem with the mass airflow sensor. Common codes are P0101, P0102, P0103 and P0104. However, a P0101 code means the signal the computer is receiving is too far below the expected value.

Most common causes of a P0101 code

The MAF sensor measures the amount of air entering the engine and the air’s density. Based on the MAF sensor readings, the ECM calculates the proper air/fuel ratio. If the O2 sensor continually reports an unexpected reading, the ECM may set a P0101 code.

1) Carboned throttle body can cause a P0101 code — This is a common cause and many DIYers don’t check this first before automatically assuming that because the mass airflow sensor is listed in the code, it must be faulty. In this case, the MAF is reporting the mass of the air entering the engine but the carbon buildup is restricting airflow into the engine. Always check for carbon buildup before suspecting a bad MAF sensor.

2) Dirty, obstructed or faulty mass air flow sensor (MAF) — The MAF sensor incorporates a hot wire or hot plate that can accumulate air filter fibers, oil or other debris that bakes onto the hot wire. That skews all further readings. In addition, leaves or other debris can get sucked into the MAF sensor and mess up the readings.

An oiled air filter is a common cause of MAF sensor failure. The oiled fibers break off from the air filter and bake onto the hot element in the MAF. Use MAF sensor cleaner to clean the hot element. If you cannot remove the baked on material, you’ll have to replace the MAF and the filter.

3) Cracked, ripped or disconnected intake boot (snorkel) can allow unmetered air into the engine — Any air that enters the engine after it has first been measure by the MAF will throw off the air/fuel mixture. A common cause of unmetered air entering the engine is a tear in the air intake duct (the rubber/plastic air duct that runs from the air filter box to the throttle body). Check the aid duct for tears or leaks.

4) Vacuum leaks (stuck open PCV valve, leaking intake gaskets, etc.) can cause a P0101 — A disconnected or cracked vacuum line can be another source of unmetered air getting into the engine. Also check for a leaking intake manifold gasket.

5) Clogged-up catalytic converter or restricted exhaust — A clogged catalytic converter or clogged muffler can prevent proper engine breathing and that can be mistaken as a faulty MAF sensor reading.

Other causes of a P0101 code

• Fuse blown to MAF — The MAF requires power and a reference voltage
• Wiring harness issues — A constant or intermittent open fault in the wiring to the MAF can cause a MAF related trouble code
• MAF sensor disconnected
• PWR GND open to MAF sensor
• A closed [throttle indication throttle position (TP) sensor system]
• Damaged MAF sensor
• Damaged PCM

How to diagnose a P0101 code

P0101 trouble codeThe sensor receives power from the fuse and ground from the PCM. Depending on the type of MAF sensor, it can alter the returning voltage or generate a digital square wave back to the computer.

A P0101 code means the computer has detected a value returning from the MAF that is outside the allowable range or of low value. The computer determines that it is a low value by comparing the reading to inputs from other sensors.

Is the P0101 trouble code serious?

The P0101 trouble code won’t prevent your vehicle from starting or driving, but if the MAF isn’t working properly, you’ll get poor gas mileage and low power.

Most common mistakes when DIYers see a P0101

DIYers commonly replace whatever part is mentioned in the trouble code. That’s a big mistake because many times the MAF is actually telling the truth. As you can see above, the two most common causes of a MAF code are a dirty MAF or an air leak in the air duct or vacuum line. Check each of those first before you jump to the conclusion that the MAF is bad.

© 2012 Rick Muscoplat

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Posted on by Rick Muscoplat



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