P0100
PowertrainMass or Volume Air Flow (MAF) Circuit Malfunction
The mass airflow (MAF) sensor circuit has a fault. The ECU isn't getting a usable signal from the sensor that measures how much air is entering the engine.
ⓘ Information only. This page provides general educational information about fault code P0100. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0100 mean?
P0100 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Mass or Volume Air Flow (MAF) Circuit Malfunction.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light
- • Rough or hesitating acceleration
- • Hard starting, sometimes worse when warm
- • Stalling at idle in some cases
- • Worse fuel economy
Possible causes
Causes commonly associated with P0100, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Failed MAF sensor (the sensing wires inside have burnt out or contaminated)
- 2. Heavily contaminated MAF, oil residue from oiled aftermarket air filters is a frequent cause
- 3. Connector unplugged, loose, or corroded
- 4. Damaged wiring between MAF and ECU
- 5. Air leak between the MAF sensor and the throttle body, unmetered air the MAF can't account for
- 6. On a few cars, ECU 5V reference fault
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Check the connector first. Then the wiring
- 2. Look at the sensing element through the MAF housing, oily film or visible contamination is your answer
- 3. Try cleaning the MAF with proper MAF cleaner (never carb cleaner, never anything else)
- 4. Read live MAF airflow values against expected at idle. Most petrol engines pull around 4-6 g/sec at idle warm; significantly off suggests sensor or air leak
- 5. Inspect the air intake boot from MAF to throttle body for splits or loose clamps
Common questions about P0100
Should I clean the MAF or just replace it? +
Try the clean first if the car has a paper or foam air filter, MAF cleaner often resolves contamination and saves a part. If the car has an oiled cotton aftermarket filter (K&N etc.) and the MAF is heavily oil-contaminated, replacement is more reliable than cleaning, the oil is hard to fully remove.
What's the difference between P0100 and P0101? +
P0100 is the broader 'circuit malfunction' code (no signal or out-of-range signal). P0101 is 'range/performance' (signal is there but the values aren't right). Same area of the system but P0101 leans more toward sensor performance, P0100 toward sensor or wiring open/short.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →