MAF sensor reading (g/s) explained

MAF (PID 10) is the measured air entering the engine, usually in grams per second. The ECU uses it to calculate fuel. If the number is wrong, fuel trims move, idle gets rough, and lean or rich codes follow.

There is no single “good” MAF number for every car. Compare idle vs RPM, and compare to a known-good similar engine — not to a forum screenshot from a different displacement.

How to read it

• Hot idle — a typical 1.8–2.4L gasoline engine often sits in the low single digits (roughly 2–7 g/s). A 5.0L idle is higher. Zero or near-zero with the engine running is a dead sensor, unplugged connector, or a tool that is not receiving the PID.
• Rev in Park — g/s should rise smoothly with RPM. A flat line while RPM climbs is a problem.
• Cruise — scales with load. A sudden drop when you accelerate is not normal.

When MAF lies

An over-reporting MAF makes the ECU add fuel (rich, negative trims, possible P0172). An under-reporting MAF looks like a vacuum leak (lean, positive trims, P0171). Oil-contaminated film on a hot-wire MAF is a common reason the number drifts after a service.

Related codes: P0101 range/performance, P0102 low input, P0103 high input.

Do not confuse MAF with a vacuum leak

Unmetered air after the MAF (cracked boot, brake booster hose) means the sensor reads “not enough air” while the engine actually gets more. Trims go positive, especially at idle. That is why you watch MAF and fuel trim together.

In MotorBit

Add MAF to the live dashboard or a chart next to RPM and STFT. If you are chasing a rough idle or sudden MPG drop, this is one of the first three PIDs to graph.