Code
P0622
Charging
Generator field / alternator control circuit malfunction
The alternator excitation control circuit has a fault.
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Most likely causes
- Faulty alternator
- Wiring fault
- Bad ECM control
Symptoms you may notice
- Charging warning light
- Battery goes flat
Checks to run
- Test the field circuit
- Test alternator output
Tools you may need
Multimeter
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.