Generator Field/F Terminal Circuit Low Voltage
The P0625 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the generator field or F terminal circuit. This circuit controls the alternator's field current, which is necessary for the alternator to produce charging voltage. A low voltage reading suggests a problem with the alternator's internal regulator, wiring, or the PCM itself, potentially leading to battery discharge and electrical system issues.
01. Most Common Causes
- Faulty alternator voltage regulator
- Open or shorted wiring in the field circuit
- Damaged alternator internal components
- Faulty PCM or connection issues
02. Symptoms You Will Notice
- Battery warning light illuminated
- Battery not charging or dead battery
- Dimming headlights or electrical issues
- Engine stalling or difficulty starting
03. Step-by-Step Diagnosis
Step 1: Use a multimeter to check battery voltage with engine off (should be ~12.6V) and running (should be ~13.5-14.5V). Low running voltage indicates charging issue.
Step 2: Inspect the alternator field circuit wiring for damage, corrosion, or loose connections. Check the F terminal voltage at the alternator with key on (should be battery voltage).
Step 3: Test the alternator output and voltage regulator using a load tester or by checking field current draw. If field circuit is open or shorted, replace alternator.
Step 4: If wiring and alternator are good, check PCM for faults or perform a PCM reset. May require reprogramming or replacement.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may stall or leave you stranded due to a dead battery. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, but if alternator replacement is needed, costs can range from $200-$600 including parts and labor.