P0100: Mass or Volume Air Flow Sensor "A" Circuit
P0100 means Mass or Volume Air Flow Sensor "A" Circuit. The mass air flow (MAF) sensor measures how much air enters the engine. The engine computer uses it to calculate fuel delivery. The control module has detected a fault in the circuit itself, such as an open circuit, a short, or a signal outside the electrical limits it expects.
Can I keep driving? Drivable with care. Diagnose soon: performance, economy or other components can be affected.
Common symptoms
- Check engine light on
- Hesitation, stumbling or surging
- Rough idle or stalling
- Poor fuel economy
- Hard starting
Possible causes
- Dirty or contaminated MAF element (often from oiled air filters)
- Air leak between the MAF sensor and the throttle body
- Damaged connector or wiring
- Failed MAF sensor
- Very dirty or collapsed air filter
How to diagnose P0100
- Inspect the intake duct after the MAF for cracks and loose clamps.
- Clean the sensor element with a dedicated MAF cleaner; never touch the element.
- Compare the MAF reading at warm idle with the expected value for the engine size.
- Check power, ground and signal at the connector.
What the code means, digit by digit
Generic codes have the same definition on every OBD-II vehicle (petrol cars from model year 1996 in the US, 2001 in the EU; diesels later). Manufacturers can add their own enhanced codes; those are not listed here.
Related codes
General guidance only. Fault codes describe what the engine computer saw, not which part failed: confirm with testing before replacing parts, and follow the vehicle's service information.