Time since engine start
How many seconds have passed since the engine started. The number says nothing on its own — it is there so you know which moment the other readings belong to: a cold engine in its first minutes behaves quite differently from a warm one. It also shows whether the car has reached closed loop: until the oxygen sensors warm up, the fuel trims sit at zero and say nothing about the mixture. It resets at every start, so in a trip recording it serves as the time axis.
What is normal
Useful when reading a freeze frame: trouble ten seconds after a start and forty minutes in are different stories.
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.
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.