What P0104 means
The mass air flow sensor (MAF) sits between the air filter and the throttle or compressor and measures how much air the engine draws in; fuel quantity, load and ignition are calculated from it.
How the engine computer detects it
Most are hot-film or hot-wire sensors that output either a voltage or, on GM, Saab and newer Ford systems, a frequency. P0104 covers brief dropouts or jumps in the signal without a permanent low or high fault – the classic sign of a loose contact. In Ford's 2020–2023 gasoline summary the code is set once more than 25 short open or short-circuit events have been counted. GM and Saab do not list P0104 in the documents checked; there such dropouts end up under P0102/P0103 or P0101. The trip count is not stated by Ford. Diagnosis means moving the harness while watching the live signal and checking terminals for corrosion and weak tension.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on, may go out again
- Occasional hesitation, misfire-like stumble, flat spot
- Intermittent rough idle or stalling
Common causes
- Loose contact at the sensor connector (corrosion, spread terminals, broken latch) Most likely
- Chafed or partly broken wire moved by the engine Possible
- Sensor electronics dropping out (temperature-dependent) Possible
- Poor ground or electrical interference Less likely
How to diagnose P0104
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: mass air flow sensor, mass air flow sensor wiring, sensor supply voltage.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 1
- Fuel and air metering
- 04
- Specific fault
Questions drivers ask
Can I drive with code P0104?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0104?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0104 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0104 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.