P0620 Generator (alternator) control circuit
What P0620 means
On many cars the engine computer controls alternator output through a control wire to its voltage regulator. P0620 means it detected a fault in that control circuit. The alternator may charge too little, too much or not at all.
P0620 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 100–800 €
- Workshop time
- 0.5–3.5 h
- Repair difficulty
- Medium
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- No
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Battery or charging warning light
- Dim or flickering lights
- Battery going flat
- Check engine light on
Common causes
- Damaged wire or corroded connector at the alternator
- Faulty alternator voltage regulator
- Failed alternator
- Poor ground between engine and body
- Engine computer fault (rare)
Can I keep driving with P0620?
You can drive for now, but have it checked within one or two weeks. If the battery warning light is on, the car may stop once the battery is flat.
What to check first
- Measure battery voltage with the engine running
- Inspect the alternator connector and control wire
- Check the engine and body ground straps
- Test the alternator and regulator and replace if faulty
Related codes
- P0627 Fuel pump control circuit/open
- P0628 Fuel pump A control circuit low
- P0615 Starter relay circuit
- P0610 Control module vehicle options error
- P0607 Control module performance
- P0606 Control module processor fault
- P0605 Internal control module read only memory (ROM) error
- P0604 Internal control module random access memory (RAM) error
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
Updated: