Powertrain, generic · Computer and auxiliary outputs

P0625 Generator Field/F Terminal Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The alternator regulator is linked to the engine module by an L (turn-on) line, an F (field) line reporting field load as a duty cycle, or on newer cars a LIN bus. P0625 means the F feedback is too low: with the engine running the regulator reports (almost) no field duty cycle – typically an open or grounded F line, or the alternator is not charging. The Saab 9-4X sets it below 3000 rpm when the duty cycle stays under 5 % for 15 s; Saab's T8 when it stays under 0.5 % for over 30 s with the L line active, and raises the idle speed. Ford's 6.8 L V10 reports it with or without the check engine light depending on the variant. GM's newer engines combine low and high in P0622.

Likely causes

F line open or shorted to ground, connector corroded
Regulator or alternator faulty or not charging (brushes, field winding)
Alternator B+ feed missing or high resistance
Engine module

Symptoms

  • Battery warning lamp on
  • Battery not or incorrectly charged, starting problems
  • Raised or fluctuating idle
  • Check engine light on some Ford variants

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€30–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

alternatorvoltage regulatorgenerator wiringengine control module

Related codes

P0626P0622P0621P0562

References: law.cornell.edu, saabwisonline.com, saabwisonline.com, roushcleantech.com.