OBD
P0623
Generator Lamp Control Circuit
What it means
P0623 means Generator Lamp Control Circuit.
Check these first
- A failed charging warning lamp
- An open or short in the lamp control circuit
- Corrosion in the lamp circuit wiring
- A failed alternator
- A faulty PCM output
What to do next
- Check the charging warning lamp and its fuse
- Inspect the lamp control circuit wiring and connectors
- Command the lamp on with a scan tool
- Test the alternator charging output
- Repair the control circuit if the lamp does not light
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.