PID 10g/s
Mass air flow (MAF)
How many grams of air per second enter the engine. The key figure for the mixture: the unit decides how much fuel to add from it, and an error here spoils everything downstream.
What is normal
Usually 2–5 g/s at idle, depending on engine size. A low reading means a dirty sensor; it is cleaned with a proper spray, not with a rag.
These figures hold for most cars, but the maker has the last word: some engines run hotter or idle higher by design.
Codes about this parameter
P0100Mass air flow circuit malfunctionP0101Mass air flow circuit range/performanceP0102Mass air flow circuit low inputP0103Mass air flow circuit high input
We have a detailed piece on thisThe MAF sensor: signs of wear and a live-data check
Step by stepFuel use went up — where to start
Codes behind this reading
If the value is out of range, the unit usually says so with one of these codes.
P0100Mass air flow circuit malfunctionP0101Mass air flow circuit range/performanceP0102Mass air flow circuit low inputP0103Mass air flow circuit high input
How it feels behind the wheel
The same fault shows itself in different ways. Each sign below says what to look at in the live data.
The engine stumblesThe engine runs unevenly, the car shakes at idle, the exhaust note stutters. On the move the pull sags and consumption rises.Idle speed huntsThe tachometer needle wanders up and down with the car standing still: 1200, then 600. Sometimes the engine nearly stalls and picks up again.Fuel consumption has gone upYou refuel noticeably more often for the same driving. The lamp is usually off — the unit thinks it is coping.It jerks under accelerationAt steady throttle everything is fine, but under acceleration the car jerks or hesitates, as if the pedal was released for a moment.The car has lost powerThe car moves, but sluggishly: flooring the throttle changes nothing, the revs climb reluctantly. Often the lamp is on as well.It stalls at idleAt the lights, or when you lift off, the engine dies. It usually restarts straight away.
How to see it
In CarScan: the Live data tab, «Start polling». The app asks the car several times per second, draws a graph and remembers the highest and lowest value of the trip.