P0100: Mass Air Flow (MAF) Circuit Malfunction
Severity: medium
What it means: P0100 means the engine computer sees an electrical problem in the mass air flow (MAF) sensor circuit. The MAF sensor sits in the intake duct after the air filter and measures how much air the engine is pulling in, so the computer can add the right amount of fuel. When the signal is missing or out of range, the engine can run poorly or stall.
Safe to drive? Usually drivable for a short time, but the engine may hesitate, idle rough or stall, especially when pulling away. Get it fixed soon.
Common symptoms
- Check engine light
- Rough idle or stalling
- Hesitation or poor power
- Worse fuel economy
Likely causes, ranked
- MAF connector loose, unplugged or corrodedDIY
- Damaged wiring to the MAF sensorShop
- Failed MAF sensorDIY
- Air leak or loose intake duct near the sensorDIY
Vehicle-specific notes
- 2000–2005 Toyota Echo: On Car Talk, a 2000 Echo owner got P0100 and P0110 right after cleaning the MAF sensor, because he hadn't pushed the connector all the way back in. The car stalled a couple of times until he reseated it. Read the full answer · Source
DIY or shop?
Usually DIY: check that the connector is pushed all the way in and the intake duct is tight. Swapping the MAF sensor is a bolt-on job on most cars. Wiring tests need a meter.
Before you replace parts
- Check that the MAF connector is fully seated and locked.
- Inspect the intake duct between the air filter and throttle body for cracks or loose clamps.
- Clear the code and see whether it comes back.
- Test the wiring and sensor signal before buying a new sensor.
Safety / mechanic note
Verify with a mechanic. Stalling when pulling into traffic is the main risk. A code points to a circuit or system, not always a specific part.