Body, generic

B0129 DC/AC Converter A High Voltage Power Outlet "C" Circuit/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

B0129 covers outlet C. Apart from wiring faults, the converter also cuts sockets on purpose when the load is too high. Ford's patent US11043801B2 gives limits of 20 A for the 120 V sockets and 30 A for the 240 V socket, and when total power exceeds the ceiling it de-energises sockets by priority, the lowest first. Ford's SSM 51498 for the 2023 Super Duty describes the resulting Pro Power Onboard Turned Off message after wattage thresholds were exceeded, which could only be cleared once the load was unplugged. A shutdown like that is not an open circuit: B0129 means the converter finds no intact path to socket C. Which socket that is, and any maker using B0129, is not public.

Likely causes

Terminal at outlet C overheated or burnt from heavy loads, contact lost
Harness to outlet C open
Switching element for outlet C inside the converter defective

Symptoms

  • Socket C stays dead even with no load connected
  • Outlet message that cannot be cleared by unplugging and resetting
  • Outlet circuits carry 120/240 V AC from a high-voltage source; work only with the system de-energised

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€60–800
Time0.5–3 h

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

Parts involved

dc ac converter ahv outlet c

Related codes

B0127B0128B012AB012BB012C

References: patents.google.com, static.nhtsa.gov.