P0101 code: mass air flow (MAF) range/performance

What each part of the code means

P: Powertrain
0: Generic code, defined by SAE
1: Fuel and air metering
01: The specific fault

P0101 and the related codes

P0100: Mass Air Flow Circuit Malfunction
P0101: Mass Air Flow Circuit Range/Performance
P0102: Mass Air Flow Circuit Low Input
P0103: Mass Air Flow Circuit High Input

How serious is it?

DeepDiag rates a stored P0100, P0101, P0102 or P0103 as major, and a pending one as pending. The rating is a starting point, not a safety check.

Possible causes

A mass air flow (MAF) sensor measures how much air the engine takes in, and the engine computer uses that reading to work out how much fuel to inject. It usually sits in the intake duct, after the air filter and ahead of the throttle body.

P0101 is a plausibility check. The computer sets it when the MAF reading doesn't make sense next to its other readings, such as throttle position and engine speed, and so doesn't match the airflow it calculates. California's OBD rules require this kind of check, which they call a rationality check, on input sensors such as the MAF where it's feasible, and require it to store a different code from a circuit fault. Circuit faults have their own codes, P0102 and P0103, but GM has traced P0101 on some of its models to a poor connection or a broken wire, so the wiring is still worth checking.

In no particular order: which one is likeliest depends on your car and its data.

A dirty or contaminated sensor: dust, dirt or oil on the sensing element skews the reading. The oil can come from an over-oiled reusable air filter, or from oily vapor drawn in through the crankcase ventilation (PCV) system.
Air leaks after the sensor: air that gets in after the MAF is never measured: a cracked or split intake boot, or a leaking intake gasket or PCV hose. On turbocharged engines, GM has also traced P0101 to charge air pipes that leak or have come off.
The sensor itself: a damaged sensing element, or one that has drifted out of calibration with wear.
Wiring and connectors: a poor or corroded connection, or a fault in the sensor's power feed or ground, can skew the signal.
Another sensor: the computer judges the MAF reading against other sensors, so a fault in one of those can set P0101 too.
Water: water drawn in through the air filter, in heavy rain for example, can foul or damage the sensor.
Engine software: some makers have released software updates for P0101 on particular models.

What to check in the data

Mass air flow: live MAF readings, where the car supports them.
Other air readings: intake manifold pressure, barometric pressure, throttle position, intake air temperature and engine load, where the car supports them.
Fuel trims: live short-term and long-term fuel trim for each bank, where the car supports them.
Freeze frame: the sensor snapshot from the moment the fault was recorded.
A recorded drive: live sensor data that you can record on a drive for the AI to review, including a guided test drive.
Other codes: a failure in one component can set a code in another, so read every stored and pending code.

Before you clear it or buy parts

Clearing erases stored and pending codes and resets the emissions readiness checks, so the car may fail an emissions test until it has been driven enough for them to complete again. If a stored code comes straight back, that points to an active fault.

Rank the possible causes by likelihood, then run the simplest, cheapest test that would confirm the cause before you buy a part. Read what to do before you clear codes.

Watch the MAF reading: it should rise smoothly as the engine speed goes up. Compare it with the maker's figures, or with known-good readings at the same engine speed.
Read the fuel trims: a dirty sensor can read high at idle and low under load, so the trims are negative at idle and positive at cruise. A vacuum leak shows a different pattern: positive trims that are highest at idle and fall as engine speed rises.
Inspect before you clean, and clean before you replace: check the air filter, and the duct between the sensor and the throttle body for tears and cracks. To clean the sensor, use a spray made for MAF sensors, not carburetor or brake cleaner, and never touch the sensing element.
Fix the source of the dirt: a cleaned or new sensor will foul again if oil from the air filter or the PCV system keeps reaching it.
Rule out a restriction: a blocked air filter or a restricted exhaust cuts the air the engine draws in, and in tests that can look like a sensor that reads low.
Don't replace the sensor on the code alone: GM tells its technicians not to replace the MAF sensor unless it is damaged or proven to be the cause, and to diagnose other stored codes first.

How DeepDiag helps

DeepDiag reads P0101 and the data above, then explains in plain language what the data shows, what the AI suspects and how confident it is. It also suggests checks to run before you buy parts, and says whether it's a job you can do yourself.

DeepDiag gives an AI-assisted reading of the data your car reports. It isn't a professional inspection, a safety check or a guarantee, and the AI can be wrong. Every feature needs an active Premium subscription.

Coming soon

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Sources

The possible causes, definitions and repair tips on this page come from these sources, checked in November 2026. What DeepDiag reads and how it rates a code come from the app itself.

P0101: mass air flow range/performance.