What does code P0621 mean?
A malfunction is detected in the alternator warning lamp (L terminal) control circuit.
OBD-II Code
P0621 — Generator Lamp L Control Circuit Malfunction
A malfunction is detected in the alternator warning lamp (L terminal) control circuit.
Common symptoms
- Battery warning light inoperative or constantly on
- irregular charging
Possible causes
- Faulty alternator
- open or shorted L circuit
- PCM fault
Initial recommendation
Inspect alternator, check continuity of L circuit and verify PCM control.
Safety notice
This information is for guidance only and does not replace a physical vehicle inspection or diagnosis by a qualified mechanic. If the vehicle has severe power loss, smoke, a fuel odor, overheating, brake or steering problems, or any unsafe behavior, avoid driving it and seek professional inspection.
Analyze this code with MecaOBD
Use the app to combine code P0621 with your vehicle's actual symptoms for more complete diagnostic guidance.
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