Powertrain, generic · Computer and auxiliary outputs

P0626 Generator Field/F Terminal Circuit High

Check engine lightOn
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. P0626 means the F feedback is too high – a duty cycle near 100 % when little or no field current is expected, typically a short to battery voltage. The Saab 9-4X sets it with ignition on and engine off above 65 % for 15 s, Saab's ME9 above 65 % for 3 s with the engine running, and raises the idle speed. Chrysler fixed P0626 on the 2019 Ram 3500–5500 chassis cab 6.7 L Cummins by reprogramming, as part of a check engine light bulletin; Ford's 6.8 L V10 reports it with or without the lamp. The former obdex title 'Performance' was wrong – all lists and manufacturers use 'High'.

Likely causes

F line shorted to battery voltage (chafing), connector
Regulator faulty (field permanently on, possibly overcharging)
Engine module software (Ram 6.7 L 2019)
Module input faulty

Symptoms

  • Battery or check engine lamp (Chrysler/Ford partly with MIL)
  • Raised idle
  • Possibly overvoltage or overcharging with a regulator fault
  • Often no driving symptoms

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–600
Time0.3–2.5 h

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

Parts involved

alternatorvoltage regulatorgenerator wiringengine control module

Related codes

P0625P0622P0621P0563

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