P0104: The mass airflow sensor signal drops out or comes and goes
Mass air flow (MAF) sensor circuit intermittent
Severity: Monitor
An intermittent airflow signal is a sensor-circuit fault with drivability effects such as poor idle and lack of power, so it is a monitor item unless the car stalls or runs poorly.
P0104 in short
P0104 means the mass airflow sensor signal is intermittent. Poor connections and damaged wiring are the usual starting points, then a contaminated or failing MAF sensor, and intake leaks or cracked hoses. Check the connector and intake hoses first. Rodent damage is common on cars that sit.
The mass airflow (MAF) sensor tells the engine computer how much air is entering the engine. P0104 is the code for a signal that is not steady: it drops out or goes erratic rather than staying at one extreme.
Because the fault comes and goes, TroubleCodes.net advises clearing the code and testing with the key on and engine off to tell a hard fault from an intermittent one, and looking at the connector first.
Besides the sensor and its wiring, the page lists cracked or brittle hoses and intake tubing, faulty EGR or PCV valves, a defective MAP sensor, and rodent damage on stored cars. While it is active the engine may run in a fallback mode with poor economy.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Poor connection or damaged wiring at the MAF sensor
Common general cause- Why it ranks here
- Wiring and poor connections head TroubleCodes.net's list, and they fit a signal that comes and goes.
- What would change this
- A connector that is corroded, loose or wiggle-sensitive raises it.
Cause 2: Contaminated or failing MAF sensor
Common general cause- Why it ranks here
- The page lists oil, dust or debris on the sensor and a defective sensor as causes; cleaning with isopropyl alcohol or contact cleaner is mentioned, with replacement sometimes needed.
- What would change this
- A dirty element, or a signal that stays erratic after cleaning, raises it.
Cause 3: Cracked intake hoses or air leaks
Common general cause- Why it ranks here
- Cracked or brittle rubber hoses and intake tubing are listed, and TroubleCodes.net says to check all vacuum lines and intake hoses.
- What would change this
- A crack or loose clamp found on the intake raises it.
Cause 5: Rodent damage on a stored vehicle
Possible — needs testing- Why it ranks here
- TroubleCodes.net lists rodent damage in stored cars.
- What would change this
- Chewed wiring or nesting material under the hood raises it.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read the freeze-frame data and recent maintenance history, then clear the code.
IfThe code returns immediately with the key on and engine off
It meansIt is closer to a hard fault in the sensor or wiring.
IfThe code only returns after driving
It meansIt is intermittent; look for loose or contaminated parts.
Step 2: Inspect the MAF connector for corrosion and look over the wiring for damage.
IfCorrosion, damage or a loose pin
It meansRepair it first.
Points to: Poor connection or damaged wiring at the MAF sensor
IfConnector and wiring look fine
It meansCheck the sensor and intake.
Step 3: Inspect the sensing element for oil or dirt and check intake hoses, tubing and vacuum lines for cracks or loose connections.
IfA cracked hose or loose clamp
It meansFix the leak.
IfThe element is dirty
It meansClean it with a suitable cleaner and see if the code returns.
IfEverything is clean and tight
It meansSuspect the sensor itself or the other listed parts.
Symptoms
- Check engine light
- Difficulty starting
- Poor idle quality
- Lack of power
- Poor fuel economy
Compare with: Rough idle with the check engine light on, Check engine light with loss of power
How to fix
Step 1: With the engine off, check that the MAF connector is fully seated and free of corrosion.
Step 2: Look over the intake hoses for cracks or loose clamps.
Parts and cost context
- Mass airflow (MAF) sensor:Check wiring and intake leaks before replacing the sensor. Labour varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for P0104 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0104 yet.
All Air metering (MAF, MAP and intake air temperature) codes
P0104 questions
Why does P0104 come and go?
The code is for an intermittent signal, so a loose connector, damaged wire or contaminated sensor that works some of the time can set it.
Can I clean the MAF sensor?
TroubleCodes.net says a contaminated sensor can be cleaned with isopropyl alcohol or contact cleaner, though replacement may be needed.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error