Network, generic

U0297 Lost Communication With AC/DC Converter Control Module B

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Converter B is a second AC/DC unit, typically an additional on-board charger that raises AC charging power when combined with the first. Patents show how such pairs are coordinated: in Porsche's US10029578B2 one charger leads and the other follows commands received over a communication link, while Hyundai's US10270273B2 has a master controller steering slave controllers for several power modules. U0297 is stored when the controlling module no longer hears unit B. The vehicle usually continues to charge with converter A alone, but at a lower rate. Because CARB wants plug-in hybrid OBD to catch charger problems that reduce charging speed, a silent B is relevant there too. No manufacturer documents U0297 publicly; Volvo's use of U0296 concerns unit A.

Likely causes

Low-voltage supply or wake-up line of charger B missing
Communication line between the converters interrupted
Software or configuration does not match the fitted charger variant
Converter B internally failed

Symptoms

  • AC charging noticeably slower than usual
  • Charging system warning

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–3,000
Time0.5–5 h

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

Parts involved

ac dc converter module bvehicle bus wiring

Related codes

U0296U0598U0597U019B

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