P0100: OBD-II code P0100 flags a fault in the mass air flow (MAF) sensor circuit — the PCM is seeing an implausible or missing airflow reading.

Symptoms

• The check engine light is illuminated and the engine may hesitate, surge at idle, or stall unexpectedly.
• Fuel economy drops noticeably because the PCM cannot accurately meter fuel without a valid MAF signal.
• Rough idle, black smoke on acceleration, and reduced power output are all typical symptoms of a MAF fault.

Common causes

• A contaminated MAF sensor element (dust, oil, or fuel residue coating the hot wire) is by far the most common cause.
• A damaged or unplugged MAF connector, or a chafed signal wire between the sensor and the PCM.
• A cracked intake air boot between the MAF and the throttle body allowing unmetered air into the engine.

What to do?

Clean the MAF sensor element with dedicated MAF cleaner (never brake cleaner — it damages the hot wire). Check the intake boot for cracks or loose clamps. Verify the connector is fully seated and wiring is intact. Read live MAF grams-per-second at idle and 2,500 RPM against factory specs. Replace the sensor if it reads out of range after cleaning.