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U012D Lost Communication With Generator A Control Module

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U012D is stored when the powertrain controller loses contact with the regulator of generator A. In many Ford models this is the smart alternator, which the PCM commands over a LIN line that it often shares with the active grille shutters; for that reason U012D usually shows up together with U0284/U0285 and U042E. Ford bulletins name the culprits: water in connector C202 (Bronco Sport 1.5 L, SSM 49496, with MIL and/or Check Charging System), LIN wire VE181 shorted to ground against a bracket of the left engine mount (F-150 2.7 L, SSM 50737). Stellantis saw the same codes on a 2019 Renegade with an exposed shutter connector. Generator B uses U012F. The battery may run down.

Likely causes

Water or corrosion in a connector of the shared LIN line (grille shutter, C202)
LIN wire chafed and shorted to ground near an engine mount bracket
Generator regulator internally faulty or without supply
Powertrain controller LIN driver faulty

Symptoms

  • Check Charging System message or battery lamp
  • MIL on in some models
  • Battery discharges, voltage unstable
  • Active grille shutter codes stored as well

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–700
Time0.5–3 h

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

Parts involved

generator a modulelin bus wiring

Related codes

U042EU012FU0284U0285

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.