P0622 — Generator Field F Terminal Circuit
Seen on: Heavy Truck
Generator Field F Terminal Circuit. Common causes: Alternator field circuit fault.
Your code rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Alternator field circuit fault
- Failed voltage regulator
- open field circuit
First moves (roadside)
- Test field circuit resistance
- replace alternator if field open
FAQ
Generator Field F Terminal Circuit. Common causes: Alternator field circuit fault.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Alternator field circuit fault. Other possibilities include Failed voltage regulator; open field circuit.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.