P0622: Generator Field/F Terminal Circuit
What to do
Have the charging voltage measured promptly. If the battery is hot, swollen or smells acrid, stop driving — that is overcharging, and it is a genuine hazard rather than an inconvenience.
What this code means
A fault on the alternator's field terminal — the circuit that controls how hard the alternator works by varying current through its rotor winding. It is the actual control input, so a fault here means output cannot be regulated.
Depending on how it fails, the result is either no charging or uncontrolled charging, and the second is the more damaging: an unregulated alternator overcharges and boils the battery. If system voltage codes are stored alongside this one, that is what is happening.
Likely causes
Start here
- Faulty alternator voltage regulator · moderate
- Faulty alternator · moderate
- Broken wire in control circuit · moderate
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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