P0626 — Problem with alternator field circuit voltage

This code points to an issue with the alternator's field or F terminal circuit showing higher voltage than expected. It usually means the engine control module is detecting abnormal electrical signals from the alternator, which can affect charging performance.

Common causes

The cause is almost always one of a few things. Here they are — P0626 rarely comes from anything outside this list:

• Faulty alternator or regulator
• Damaged or corroded wiring/connectors at alternator
• Loose or poor battery connections
• Blown fusible link or fuse in charging circuit
• Faulty engine control module (rare)

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Check and clean battery terminals and cables
2. Inspect wiring and connectors at alternator for damage
3. Test alternator output and regulator function
4. Replace alternator if faulty
5. Check and replace fuses or fusible links if needed

That is what holds for P0626 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.