Network, generic

U027B Lost Communication With Battery Charger Control Module D

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U027B refers to a fourth charger unit. In multi-charger designs the units also split the control task; in a dual charger system patented by Lear, two chargers feed the battery in parallel, one regulating voltage and the other regulating current. If one partner falls silent, the remaining unit has to carry the job alone or charging is stopped. U027B is set when the supervising controller loses all messages from charger D, whereas U057C stands for messages from D that arrive but fail checks. No manufacturer documents U027B or a fourth on-board charger publicly. The CARB rule for plug-in hybrids exempts charging faults that cannot be told apart from a supply problem outside the car. Expect slower or interrupted charging.

Likely causes

Low-voltage supply, fuse or wake-up of charger D missing
Bus wiring to charger D damaged or connector wet
Charger D control board faulty

Symptoms

  • Charging power lower than usual
  • Charging session aborted with a warning

Repair estimate

DifficultyHardWorkshop job
Parts and labour€0–2,500
Time0.5–4 h

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

Parts involved

on board chargervehicle bus wiring

Related codes

U027AU057CU019BU01BB

References: patents.google.com, law.cornell.edu.