What it means
The ECU detects intermittent signal dropouts or noise on the mass air flow (MAF) sensor circuit. The fault is not constantly present, suggesting a loose connection, intermittent wiring break, or a failing sensor under specific conditions (vibration, temperature).
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The MAF sensor measures incoming air, and the ECM watches its signal to calculate engine load and fueling. P0104 sets when that signal drops out or becomes noisy intermittently, so the fault may appear only with vibration, heat, or particular driving conditions.
Common causes
Most likely first.
- MAF connector loose or corroded
- Wiring chafed against engine components
- MAF sensor failing intermittently
Symptoms
- Check engine light on
How to diagnose it
- Review freeze-frame and pending-code data, then graph live MAF readings while gently changing engine speed to look for sudden dropouts.
- With the engine off, inspect the MAF connector for looseness, corrosion, or damaged pins and trace the harness for chafing or a break near moving or hot parts.
- With the engine idling, carefully move the accessible harness and connector while watching live data for a signal interruption.
- Check circuit power, ground, and signal continuity, flexing the harness where safe, and compare results with the wiring diagram and manufacturer's specification.
- Inspect the sensor for contamination and verify its mounting and intake duct connections.
- If the circuit remains stable but the signal still cuts out under repeatable conditions, replace the intermittently failing MAF sensor.
Common fixes
- Secure a loose MAF connector and repair corroded or damaged terminals.
- Repair chafed or broken MAF wiring and secure the harness away from hot or moving parts.
- Clean a contaminated MAF element with suitable MAF cleaner, following the product instructions.
- Replace a MAF sensor that continues to drop out after its wiring and connector test correctly.
Can I keep driving?
If the engine runs normally, drive gently and avoid hard acceleration until the intermittent fault is found. A dropout can cause sudden hesitation or stalling, so stop if those symptoms occur.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.