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Home / DTC / P0625 — Generator Field/F Terminal Circuit Low

P0625 — Generator Field/F Terminal Circuit Low

Detailed page for trouble code P0625.

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Code

P0625

Generic P — Powertrain

Generator Field/F Terminal Circuit Low

Brand: Generic
Type: P — Powertrain
Views: UK: 36 EN: 63 RU: 68
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open, short to ground, or high-resistance in the field (F) wire or connector
  • Poor connector contact, corrosion, bent pins or damaged insulation at alternator/ECM connectors
  • Faulty alternator internal regulator, brushes, rotor windings or slip rings
  • Faulty ECM/alternator control module driving the field terminal
  • Blown fuse or fusible link in the charging control circuit
  • Battery with very low state of charge, bad terminals or poor ground that affects sensing

Symptoms

  • Battery warning lamp illuminated or charging-system warning on dash
  • Low charging voltage at battery (battery not getting above ~12.4–13 V while running)
  • Dim headlights or reduced electrical performance at idle
  • Battery discharging, slow cranking or no charge after engine start
  • Multiple charging-related trouble codes present

What to check

  • Scan for freeze frame data and related codes; check pending codes
  • Confirm battery state of charge and battery terminal/ground condition
  • Measure battery voltage with engine off and running at idle and with increased RPM/load
  • Backprobe the alternator F terminal with key ON engine OFF and with engine running
  • Visually inspect F-wire, connector pins and harness for damage or corrosion
  • Check continuity and resistance of F circuit between alternator and PCM/ground (engine off, battery disconnected when measuring resistance)

Signal parameters

  • Key ON, engine OFF: F terminal may be battery voltage or a commanded reference voltage depending on system (expect ~0–12 V depending on design)
  • Engine running (idle): F terminal voltage or PWM duty will vary as system regulates charging — typically changes with load and RPM
  • Field coil resistance (alternator-specific): low ohms (typically under a few ohms) — consult vehicle/service data for exact value
  • Charging voltage at battery while running: normally ~13.5–14.8 V on healthy system

Diagnostic algorithm

  1. Retrieve freeze frame, all related codes and service information specific to the vehicle. Check for intermittent flags.
  2. Verify battery condition and clean/tighten battery terminals and engine/chassis grounds.
  3. With ignition ON (engine OFF) backprobe the F terminal at the alternator connector. Note voltage. If zero or very low where a control voltage is expected, proceed to wiring checks.
  4. Start engine and measure F-terminal voltage or PWM duty while observing charging voltage at the battery. Compare to expected behavior from service manual.
  5. Inspect and wiggle wiring and connectors between alternator and PCM while monitoring F-terminal signal for intermittent changes.
  6. Check continuity and resistance of the F circuit to the PCM and to ground. Repair any open/high-resistance sections (repair/replace wiring or connector as required).
  7. Verify generator B+ output and perform an alternator bench test or swap with known-good unit if wiring/ECM tests are inconclusive.
  8. Check/replace any blown fuse or fusible link protecting the field/control circuit.
  9. If wiring and alternator internals test good, test or replace the ECM/alternator control module per manufacturer procedure.
  10. Clear codes and retest under the same conditions to confirm repair.

Likely causes

  • Damaged/loose F-terminal connector at alternator
  • Worn alternator brushes or internal regulator failure
  • Open or short in field control wire between alternator and PCM
  • Corroded battery or engine ground reducing circuit reference

Fault status

⚠️ Status
Control module detected low voltage/current on the alternator generator field (F) terminal — charging may be reduced or disabled.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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Code

P0625

HUMMER P — Powertrain

Generator F-Terminal Circuit Low Voltage

Brand: HUMMER
Type: P — Powertrain
Views: UK: 25 EN: 52 RU: 57
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open, short to ground, or high-resistance in the field (F) wire or connector
  • Poor connector contact, corrosion, bent pins or damaged insulation at alternator/ECM connectors
  • Faulty alternator internal regulator, brushes, rotor windings or slip rings
  • Faulty ECM/alternator control module driving the field terminal
  • Blown fuse or fusible link in the charging control circuit
  • Battery with very low state of charge, bad terminals or poor ground that affects sensing

Symptoms

  • Battery warning lamp illuminated or charging-system warning on dash
  • Low charging voltage at battery (battery not getting above ~12.4–13 V while running)
  • Dim headlights or reduced electrical performance at idle
  • Battery discharging, slow cranking or no charge after engine start
  • Multiple charging-related trouble codes present

What to check

  • Scan for freeze frame data and related codes; check pending codes
  • Confirm battery state of charge and battery terminal/ground condition
  • Measure battery voltage with engine off and running at idle and with increased RPM/load
  • Backprobe the alternator F terminal with key ON engine OFF and with engine running
  • Visually inspect F-wire, connector pins and harness for damage or corrosion
  • Check continuity and resistance of F circuit between alternator and PCM/ground (engine off, battery disconnected when measuring resistance)

Signal parameters

  • Key ON, engine OFF: F terminal may be battery voltage or a commanded reference voltage depending on system (expect ~0–12 V depending on design)
  • Engine running (idle): F terminal voltage or PWM duty will vary as system regulates charging — typically changes with load and RPM
  • Field coil resistance (alternator-specific): low ohms (typically under a few ohms) — consult vehicle/service data for exact value
  • Charging voltage at battery while running: normally ~13.5–14.8 V on healthy system

Diagnostic algorithm

  1. Retrieve freeze frame, all related codes and service information specific to the vehicle. Check for intermittent flags.
  2. Verify battery condition and clean/tighten battery terminals and engine/chassis grounds.
  3. With ignition ON (engine OFF) backprobe the F terminal at the alternator connector. Note voltage. If zero or very low where a control voltage is expected, proceed to wiring checks.
  4. Start engine and measure F-terminal voltage or PWM duty while observing charging voltage at the battery. Compare to expected behavior from service manual.
  5. Inspect and wiggle wiring and connectors between alternator and PCM while monitoring F-terminal signal for intermittent changes.
  6. Check continuity and resistance of the F circuit to the PCM and to ground. Repair any open/high-resistance sections (repair/replace wiring or connector as required).
  7. Verify generator B+ output and perform an alternator bench test or swap with known-good unit if wiring/ECM tests are inconclusive.
  8. Check/replace any blown fuse or fusible link protecting the field/control circuit.
  9. If wiring and alternator internals test good, test or replace the ECM/alternator control module per manufacturer procedure.
  10. Clear codes and retest under the same conditions to confirm repair.

Likely causes

  • Damaged/loose F-terminal connector at alternator
  • Worn alternator brushes or internal regulator failure
  • Open or short in field control wire between alternator and PCM
  • Corroded battery or engine ground reducing circuit reference

Fault status

⚠️ Status
Control module detected low voltage/current on the alternator generator field (F) terminal — charging may be reduced or disabled.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0621 P0622 P0623 P0626 P0627 P0562
Repair manuals

Manual library for HUMMER

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Code

P0625

LAND ROVER P — Powertrain

Generator Field Terminal - Low Circuit

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 20 EN: 48 RU: 51
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open, short to ground, or high-resistance in the field (F) wire or connector
  • Poor connector contact, corrosion, bent pins or damaged insulation at alternator/ECM connectors
  • Faulty alternator internal regulator, brushes, rotor windings or slip rings
  • Faulty ECM/alternator control module driving the field terminal
  • Blown fuse or fusible link in the charging control circuit
  • Battery with very low state of charge, bad terminals or poor ground that affects sensing

Symptoms

  • Battery warning lamp illuminated or charging-system warning on dash
  • Low charging voltage at battery (battery not getting above ~12.4–13 V while running)
  • Dim headlights or reduced electrical performance at idle
  • Battery discharging, slow cranking or no charge after engine start
  • Multiple charging-related trouble codes present

What to check

  • Scan for freeze frame data and related codes; check pending codes
  • Confirm battery state of charge and battery terminal/ground condition
  • Measure battery voltage with engine off and running at idle and with increased RPM/load
  • Backprobe the alternator F terminal with key ON engine OFF and with engine running
  • Visually inspect F-wire, connector pins and harness for damage or corrosion
  • Check continuity and resistance of F circuit between alternator and PCM/ground (engine off, battery disconnected when measuring resistance)

Signal parameters

  • Key ON, engine OFF: F terminal may be battery voltage or a commanded reference voltage depending on system (expect ~0–12 V depending on design)
  • Engine running (idle): F terminal voltage or PWM duty will vary as system regulates charging — typically changes with load and RPM
  • Field coil resistance (alternator-specific): low ohms (typically under a few ohms) — consult vehicle/service data for exact value
  • Charging voltage at battery while running: normally ~13.5–14.8 V on healthy system

Diagnostic algorithm

  1. Retrieve freeze frame, all related codes and service information specific to the vehicle. Check for intermittent flags.
  2. Verify battery condition and clean/tighten battery terminals and engine/chassis grounds.
  3. With ignition ON (engine OFF) backprobe the F terminal at the alternator connector. Note voltage. If zero or very low where a control voltage is expected, proceed to wiring checks.
  4. Start engine and measure F-terminal voltage or PWM duty while observing charging voltage at the battery. Compare to expected behavior from service manual.
  5. Inspect and wiggle wiring and connectors between alternator and PCM while monitoring F-terminal signal for intermittent changes.
  6. Check continuity and resistance of the F circuit to the PCM and to ground. Repair any open/high-resistance sections (repair/replace wiring or connector as required).
  7. Verify generator B+ output and perform an alternator bench test or swap with known-good unit if wiring/ECM tests are inconclusive.
  8. Check/replace any blown fuse or fusible link protecting the field/control circuit.
  9. If wiring and alternator internals test good, test or replace the ECM/alternator control module per manufacturer procedure.
  10. Clear codes and retest under the same conditions to confirm repair.

Likely causes

  • Damaged/loose F-terminal connector at alternator
  • Worn alternator brushes or internal regulator failure
  • Open or short in field control wire between alternator and PCM
  • Corroded battery or engine ground reducing circuit reference

Fault status

⚠️ Status
Control module detected low voltage/current on the alternator generator field (F) terminal — charging may be reduced or disabled.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0621 P0622 P0623 P0626 P0627 P0562
160

Browse 160 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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