Code B0129 indicates an open circuit detected in the high-voltage power outlet C circuit of the DC-AC converter (inverter) system, typically found in hybrid or electric vehicles. This fault suggests the vehicle's control module has lost electrical continuity with a specific auxiliary power outlet used to supply AC voltage to external devices. The system disables the affected outlet to prevent electrical hazards until the circuit integrity is restored.
The most common cause is a failed fuse protecting the specific AC outlet circuit due to an overload or shorted device. Inspecting and replacing the designated fuse often resolves the open circuit condition immediately.
Internal contacts within the physical outlet socket can corrode, break, or wear out, creating an open circuit. Physical damage from plugging in incompatible or forceful connectors frequently leads to this failure.
Wires leading to the outlet may be severed, chafed, or disconnected, particularly in areas subject to movement or vibration. Corrosion at the electrical connectors can also interrupt the circuit path.
The internal switching component within the inverter responsible for energizing Outlet C may have failed open. This requires specialized testing to distinguish from external wiring issues.
While rare, the control module itself may have an internal fault preventing it from detecting the circuit status correctly. This is considered a last-resort diagnosis only after all external components and wiring are verified intact.
The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:
Typically no, as this code affects an auxiliary accessory outlet rather than the primary propulsion system, though the vehicle may limit some high-voltage functions as a safety measure.
No, replacing the computer is rarely the solution for this code; the fault is almost always a blown fuse, a bad outlet socket, or damaged wiring.
You can clear the code with a scanner, but it will likely return immediately if the open circuit condition persists, as the system continuously monitors the outlet.
Repeated fuse failures usually indicate a short circuit in the wiring harness or a faulty device being plugged into the outlet that draws excessive current.