01 How Adaptive Cruise Control Actually Works • 02 Understanding Why Cars Shut Off While Driving and Ensuring … • 03 The Secret Role Of Oxygen Sensors And How They Quietly Wast… • 04 Why Your Garage Has Customers But No Profit • 05 How a Failed Deal With Honda Pushed Nissan Into Toyota’s Ar… • 06 Why Do Car Engines Have a Redline and What Happens If You E… • 07 When Reconnecting The Battery, Which Terminal is Connected … • 08 Drivers Are Only Just Discovering Why Their Cars Randomly S… • 09 The Connection Between Oxygen Sensors and Catalytic Convert… • 10 How to Increase Horsepower in a Naturally Aspirated Engine •

DTC codes / P06xx · Computer and output circuits / P0625

P0625Generator Field/F Terminal Circuit Low

P0625 means the engine computer has detected an abnormally low voltage on the generator's field or 'F' terminal circuit, which is the feedback line the voltage regulator uses to report how hard the alternator is working. The computer expects a signal that rises and falls with charging demand, and a sustained low reading tells it the circuit is grounded, open, or the regulator is not responding.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Battery warning light illuminated on the dashboard
  • Charging system gauge reading low or fluctuating
  • Dimming headlights or interior lights at idle
  • Battery going flat overnight or after short drives
  • Electrical accessories such as radio or climate control behaving erratically
  • Often no symptoms besides the warning light when the fault is intermittent

Common causes, most likely first

  1. Damaged, chafed, or corroded wiring in the generator field/F terminal circuit
  2. Failed voltage regulator inside the alternator
  3. Loose or oxidized connector at the alternator field terminal
  4. Poor ground connection between the engine block and chassis
  5. Faulty engine computer driver circuit for the field terminal
  6. Aftermarket alarm or remote starter tapped into the charging circuit

How to diagnose and fix it

  1. Inspect the field/F terminal wiring and connector at the alternator for chafing, corrosion, and tight fit
  2. Measure voltage on the field circuit with the key on and engine running, comparing to the service specification
  3. Perform a voltage drop test on the ground straps between engine, chassis, and battery negative
  4. Check charging output at the battery with a load tester to confirm the alternator is actually underperforming
  5. Disconnect the alternator and recheck the field circuit voltage to isolate a shorted regulator from a wiring fault
  6. Repair or replace the damaged section of field circuit wiring and clear the code
  7. If the circuit tests good, replace the alternator or voltage regulator as a unit and retest the charging system

What the field terminal circuit is really telling you

  • A low field terminal signal does not automatically mean the alternator is bad, because a simple chafed wire or corroded connector can pull the voltage down and mimic a failed regulator.
  • Many technicians replace the alternator only to find the code returns because the ground strap between the engine and chassis was the real culprit all along.
  • Intermittent P0625 codes often appear after a jump start or battery replacement, when a loose terminal or a spike confused the voltage regulator's feedback signal.
  • Some vehicles use a duty-cycle signal on the field circuit rather than a simple analog voltage, so a meter reading that looks low may actually be normal for that charging strategy.
  • Aftermarket accessories wired into the charging circuit can backfeed the field terminal and set this code even though the factory alternator is functioning correctly.

Can I keep driving with P0625?

You can usually drive a short distance to a repair shop, but avoid long trips, heavy electrical loads, and night driving because the battery may not be recharged and the vehicle could stall or leave you stranded. If the battery light is on and the charging gauge is dropping, stop and arrange a jump start or tow rather than continuing.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage