P0100: Mass or Volume Air Flow "A" Circuit
The engine computer has lost a usable signal from the mass airflow (MAF) sensor or sees an electrical fault in its circuit.
What P0100 means
The mass airflow sensor sits between the air filter and the throttle body. It measures how much air the engine is pulling in so the computer can calculate fuel and spark timing. P0100 is a general circuit code: the computer sees a signal that is erratic, missing or not plausible from an electrical point of view. RepairPal lists unplugged sensors, damaged wiring and corroded terminals as the common triggers, and warns that many MAF sensors are replaced when the real problem was the connector or harness. Without good airflow data, the computer falls back on estimates, so the engine may idle rough, hesitate or stall. Shops check freeze frame data and watch the MAF grams per second reading as RPM changes. A quick test RepairPal describes is comparing the barometric reading the computer calculates against your real elevation. Then they test power, ground and signal at the connector. Fix it soon so the engine is not running on rough guesses.
Common symptoms
- Check engine light on
- Engine runs poorly or idles rough
- Stalling or hesitation on acceleration
- Poor gas mileage
- Sometimes no noticeable symptoms
Most common causes
- MAF sensor unplugged or damaged wiring
- Loose or corroded MAF connector terminals
- Failed MAF sensor
- Blown fuse or bad power feed to the sensor
- Air leak or loose intake boot affecting the reading
What to check yourself first
Check that the MAF connector is clicked in and the pins are clean. Look for a damaged wire near the air box. Make sure the air filter box is closed and the intake boot is tight. Clear the code and see whether it comes back.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | RepairPal lists a bad connector or harness as a common reason the MAF gets replaced for nothing. |
| Clean the MAF sensor yourself | $15-$20 | Worth trying if the sensor element is dirty, about $17 for a can of cleaner. |
| Replace mass airflow (MAF) sensor | $274-$381 | When the sensor fails voltage or frequency tests with good power and ground. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0101 Mass or Volume Air Flow "A" Circuit Range/Performance
- P0102 Mass or Volume Air Flow "A" Circuit Low
- P0103 Mass or Volume Air Flow "A" Circuit High
- P0171 System Too Lean (Bank 1)
- P0113 Intake Air Temperature Sensor 1 Circuit High