OBD Code P0100: Mass Air Flow Circuit Malfunction — Connector First

What does code P0100 mean?

Code P0100 (Mass Air Flow Circuit Malfunction) means the ECU is receiving no valid signal from the MAF sensor — either the circuit is open, or the reading is completely out of range. This is more severe than P0101 (performance issue) — the circuit is fundamentally broken.

Symptoms

• Check engine light
• Very difficult or impossible starts
• Severe power loss, limp mode
• Engine may stall repeatedly
• Heavily increased fuel consumption

Step-by-step diagnosis

1. Check the MAF connector first (free) Unplug and replug the MAF connector. Clean terminals with contact spray. Reconnect, clear code, test drive.

2. Clean the MAF sensor 👉 MAF sensor cleaner on Amazon UK — £8-12. Never use brake cleaner or WD-40 on the hot wire.

3. Check the air filter A severely blocked filter can create a vacuum that triggers P0100. 👉 Air filter on Amazon UK

4. Inspect wiring between MAF and ECU Check for chafed or melted wires, especially near hot components.

5. Test MAF with a scanner With engine warm at idle, MAF should read 6-10 g/s on a 1.4L engine. Zero or wildly fluctuating = sensor faulty. 👉 OBD2 scanner on Amazon UK

6. Replace MAF sensor 👉 Bosch MAF sensor on Amazon UK — use branded sensor (Bosch, Delphi, Hitachi)

Repair cost