P0620
Generator Control Circuit
Moderate· Fix soonIntermediatePowertrainGeneric, all makes
What it means
The ECU has detected a fault in the circuit it uses to control the alternator (generator) output.
Is it safe to drive?
The battery may not charge. Get it checked before you are stranded.
Symptoms
- Battery warning light
- Low or high charging voltage
Probable causes
Most likely first
- 1Faulty alternator
- 2Damaged alternator connector or wiring
- 3ECU fault (rare)
How to diagnose it
Work through these in order before buying parts
- 1Measure charging voltage with the engine running.
- 2Inspect the alternator connector.
- 3Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.
Common fixes
- Replace the alternator
- Repair wiring
This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.