What Does P0625 Mean?
The PCM has detected that the generator (alternator) field terminal circuit voltage is below the expected threshold. This circuit controls the alternator's output by regulating current flow through the rotor field winding. A low signal indicates the PCM cannot properly command the alternator to increase charging output, which may lead to undercharging of the battery.
Common Causes
35%
Damaged or corroded wiring/connectors in the generator field circuit
30%
Faulty alternator with internal field winding failure
20%
Failed voltage regulator (internal or external)
15%
PCM driver circuit failure for generator field control
Diagnostic Steps
1
Step 1: With KOEO, backprobe the generator field terminal connector and measure voltage — expect battery voltage when PCM commands field ON. If less than 1V, circuit is shorted to ground.
2
Step 2: Disconnect the alternator field connector and measure resistance of the field winding across the alternator terminals — expect 2-6 ohms. Infinite resistance indicates an open field winding.
3
Step 3: Inspect the wiring harness from the PCM to the alternator field terminal for chafing, corrosion, or shorts to ground. Repair as needed.
4
Step 4: With the connector disconnected from the alternator, use a DVOM to verify the PCM is outputting a proper duty-cycle signal on the field control wire — use frequency/duty cycle mode.
5
Step 5: If PCM output is correct and wiring is intact, replace the alternator assembly.
Estimated Repair Cost
$100 - $650
Parts + labor, varies by vehicle and location
The PCM has detected that the generator (alternator) field terminal circuit voltage is below the expected threshold. This circuit controls the alternator's output by regulating current flow through the rotor field winding. A low signal indicates the PCM cannot properly command the alternator to incr...
The most common cause of P0625 (Generator Field/F Terminal Circuit Low) is: Damaged or corroded wiring/connectors in the generator field circuit
Typical repair costs for P0625 range from $100 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience battery drain and eventual stalling if the charging system cannot maintain proper voltage. Avoid long trips until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0625 to identify the root cause.
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Quick Info
Category
Powertrain
System
Charging System
Difficulty
Type
Generic (SAE)
Recommended Tools
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