What P0100 means
The mass air flow sensor (MAF) sits between the air filter and the throttle or compressor and measures how much air the engine draws in; fuel quantity, load and ignition are calculated from it.
How the engine computer detects it
Most are hot-film or hot-wire sensors that output either a voltage or, on GM, Saab and newer Ford systems, a frequency. P0100 means the control module gets no usable signal at all. Ford uses it for a broken sensing element on digital sensors (period longer than 1.3 ms, i.e. below about 0.78 kHz, for half a second); on GM's 3.0 V6 in the Saab 9-4X it is set at 0 Hz. Many systems with voltage sensors skip P0100 and report low or high directly. The engine then runs on air mass calculated from manifold pressure, throttle angle and speed; Ford also disables start-stop.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Rough idle, hesitation, lack of power (substitute value)
- Hard starting or stalling
- Higher fuel consumption
Common causes
- Connector unplugged or corroded, signal or supply wire open Most likely
- Sensor faulty internally (broken element, failed electronics) Most likely
- Supply fuse or relay failed Possible
- Control module input faulty Less likely
How to diagnose P0100
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: mass air flow sensor, mass air flow sensor wiring, sensor supply voltage.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 1
- Fuel and air metering
- 00
- Specific fault
Questions drivers ask
Can I drive with code P0100?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0100?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0100 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0100 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.