P0101: the airflow sensor reading doesn't add up
The mass airflow sensor sits in the intake pipe and measures how much air is actually flowing into the engine, which the engine control unit uses to work out how much fuel to add. This code means the sensor's reading doesn't make sense against the engine's other signals, such as engine speed and throttle position, even though the signal itself looks electrically fine. It's a plausibility fault: the number the sensor is sending isn't impossible, just not one the computer believes.
You might notice
- The engine warning light comes on
- The engine may idle unevenly or hesitate under acceleration
- mass airflow sensor
- — a sensor in the intake pipe that measures how much air is entering the engine
What the code itself says
P0101 is a powertrain (engine, gearbox and drive system) code, and the 0 after the letter means it is a generic code with a standard meaning.
Grouped here as: Engine running, fuelling and misfires — Air metering, fuelling, ignition, misfire, idle, boost, knock, oxygen sensors and the catalyst, all working together in the running engine. That grouping is ours, to help explain the code. The code's official family is the letter at the start.
This page is generic. Your car isn't.
A code on its own only tells you what the sensor saw, not what's actually wrong — and that changes next to your other codes. Read this one together with the rest of your scan and we'll work out what's really going on.
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