PID 42V
Control module voltage
System voltage.
What is normal
13.8–14.6 V with the engine running. Lower — the alternator; higher — the regulator.
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 thisGeely over OBD-II: what answers and what stays silent
Codes behind this reading
If the value is out of range, the unit usually says so with one of these codes.
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 voltage jumps, the lights dimThe headlights and the dashboard change brightness while driving, sometimes the battery lamp flickers. The electronics behave oddly.The steering has gone heavyThe wheel turns noticeably harder than usual, especially when parking and at low speed. Sometimes the assistance returns after restarting the engine, sometimes it disappears entirely.Will not start in ParkIn P the starter is silent, but in N the car starts. Or the other way round. Sometimes every gear letter lights up at once; sometimes cruise control will not engage.It cranks but will not startThe starter turns the engine over briskly, but it does not catch. Sometimes it catches and dies.It stalls at idleAt the lights, or when you lift off, the engine dies. It usually restarts straight away.Check engine came on after a wash or heavy rainYou washed the car or drove through a downpour — and the light came on. It often clears itself in a day or two.
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.