P0622: Generator field F control: circuit fault
The ECU detects a fault in the F circuit, which controls the alternator’s field excitation. Usually wiring, the plug or the alternator.
| Code | P0622 |
|---|---|
| System | Engine and transmission |
| Group | P06xx, Control unit and auxiliary outputs |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0622 means
The alternator produces more or less current depending on how strongly its internal coil, the field, is energised. On many cars the ECU controls that field through the F circuit. This code means that circuit has a fault, so the alternator may undercharge or overcharge.
Most common causes
- Alternator plug loose, dirty or corroded
- F circuit wire broken, chafed or shorted
- Worn alternator brushes or regulator
- Faulty alternator
- Poor alternator or engine earth
Symptoms
- Engine warning light on, sometimes with the battery light
- Battery going flat or voltage too high
- Lights changing brightness
Can you drive with P0622?
With care You can drive, but there is a risk of a flat or overcharged battery. Get it checked soon.
Open the bonnetthe in-depth explanation
How to check it
With the engine running, watch the control module voltage on the scan tool and switch on the lights and fan: it should stay around 13.5 to 14.5 volts. If it drops below 13 or goes above 15, the alternator is not regulating properly.
How to read and clear P0622 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0622 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P061E The internal control unit brake signal gives readings outside the normal range
- P061F The internal control unit throttle actuator controller gives readings outside
- P0620 Generator control: circuit fault
- P0621 Generator lamp L control: circuit fault
- P0623 The generator light control has an electrical fault
- P0624 The circuit controlling the fuel filler cap warning lamp has a fault
- P0625 The generator field terminal gives a lower signal than normal
- P0626 The generator field terminal gives a higher signal than normal
- P0600 Serial communication link fault
- P0601 Internal control module memory checksum error
- P0602 Control module programming error
- P0603 Internal control module keep alive memory (KAM) error
What does code P0622 mean?
The alternator produces more or less current depending on how strongly its internal coil, the field, is energised. On many cars the ECU controls that field through the F circuit. This code means that circuit has a fault, so the alternator may undercharge or overcharge.
Can you drive with P0622?
You can drive, but there is a risk of a flat or overcharged battery. Get it checked soon.
How do you clear P0622?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0622 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
