P0620Powertrain
Generator control circuit — malfunction
Where to start
The control unit cannot command the alternator. Check the connector on the alternator and its wire: they are more often at fault than the alternator itself. A symptom you can see without tools is under 13.5 volts at the battery with the engine running.
A code is not a diagnosis. It says which check failed, not which part to replace. Clearing it without repair only means the car will report it again in a few trips.
How to put together a report a mechanic will actually read
We have a detailed piece on thisCharging and voltage: P0560, P0561, P0620, P0621, P0622
How the code is built
Letter — the systemPowertrain: engine and transmission
Common or the maker's ownGeneric code: the same on every car
Which part of the engineControl module and its circuits
Number of the faultThe serial number inside that group — it does not say how serious the fault is
All codes in «Control module and its circuits»
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.
How the app helps
CarScan reads this code from your car through an OBD-II adapter, shows whether it is active now or only stored, names the module that reported it, and puts it into a plain-text report for your mechanic.