P0620: the alternator's control circuit has a fault
On many cars the engine control unit, rather than the alternator alone, decides how hard the alternator should work at any moment, sending it commands over a control circuit to balance charging against fuel use and engine load. This code means that control circuit isn't behaving the way the computer expects. It covers the wiring and connector as much as the alternator itself.
You might notice
- The engine warning light comes on, sometimes alongside a battery warning light
- The battery may not charge properly, or electrical items may seem underpowered
- alternator
- — the part that generates electricity while the engine runs, keeping the battery topped up
What the code itself says
P0620 is a powertrain (engine, gearbox and drive system) code, and the 0 after the letter means it is a generic code with a standard meaning.
Grouped here as: Charging and system voltage — System voltage and charging. That grouping is ours, to help explain the code. The code's official family is the letter at the start.
This page is generic. Your car isn't.
A code on its own only tells you what the sensor saw, not what's actually wrong — and that changes next to your other codes. Read this one together with the rest of your scan and we'll work out what's really going on.
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