PID 04%
Calculated engine load
How hard the engine is working right now, as a share of what it could give at these revs. The figure is calculated: the unit works it out from air, revs and fuelling — there is no load sensor in the car.
What is normal
15–25 % at idle, 25–60 % at a steady cruise. High load at idle means the engine struggles even to turn itself: look for a leak, a blocked exhaust or extra drag.
These figures hold for most cars, but the maker has the last word: some engines run hotter or idle higher by design.
We have a detailed piece on thisIntake manifold runner flaps: P2004, P2006, P2008, P2015
Step by stepUnstable idle — how to find the cause
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.
It stalls while drivingThe engine dies while the car is moving — at speed, in a corner or when lifting off. The steering and brakes go heavy at once.The revs are capped and the car will not accelerateThe pedal is flat to the floor but the engine caps out around three thousand and goes no further. The car moves, but sluggishly, and overtaking is impossible. The check light is often on.Fuel consumption has gone upYou refuel noticeably more often for the same driving. The lamp is usually off — the unit thinks it is coping.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.
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.