The P0621 trouble code indicates a malfunction in the generator lamp control circuit. This code is typically associated with issues related to the vehicle’s charging system and the control of the generator warning lamp on the dashboard.
P0621 Generator Lamp “L” Control Circuit Malfunction
Code symptoms P0621.
1. Check Engine Light (CEL) illuminated on the dashboard.
2. Generator warning lamp (battery light) may illuminate on the dashboard.
3. Difficulty starting the vehicle.
4. Dimming or flickering of interior or exterior lights.
5. Battery not charging properly.
6. Possible loss of electrical power while driving.
This code is common in brands such as:: Chevrolet, Renault, Ford, Toyota, Nissan, Mercedes Benz, Honda.
Causes of the code P0621.
1. Faulty generator (alternator).
2. Defective voltage regulator.
3. Wiring issues, such as short circuits or open circuits, in the generator lamp control circuit.
4. Loose or corroded electrical connectors related to the generator or generator lamp.
5. Blown fuses related to the charging system.
6. Faulty battery.
Code Solutions P0621.
1. Inspect the generator and voltage regulator for any signs of damage or wear. Replace components as needed.
2. Check the wiring and connectors associated with the generator lamp control circuit for any signs of damage, corrosion, or looseness. Repair or replace wiring and connectors as needed.
3. Test the battery to ensure it is in good condition and holding a charge. Replace the battery if necessary.
4. Verify that all fuses related to the charging system are intact. Replace any blown fuses.
5. Clear the trouble codes and test drive the vehicle to see if the P0621 code returns. If it does, further diagnosis may be necessary.