P0104: the airflow sensor circuit cuts in and out
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 that sensor's circuit signal comes and goes, or briefly drops out and returns, rather than failing steadily in one direction. It's an intermittent fault, which can make it harder to catch on a single check because it isn't present all the time.
You might notice
- The engine warning light comes on
- The engine may hesitate or run unevenly, on and off rather than all the time
- mass airflow sensor
- — a sensor in the intake pipe that measures how much air is entering the engine
What the code itself says
P0104 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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