Thermador Range Error Code F143

The F143 error code on a Thermador range indicates an open circuit condition on the Vcc supply line feeding the slave microcontroller. Vcc refers to the regulated DC supply voltage that powers the secondary (slave) microprocessor on the Display Board. When this voltage line is interrupted or fails to reach the slave micro, the control system detects the absence of that supply and triggers the F143 fault. An open circuit means the electrical path is broken somewhere between the Power Board, the interconnecting wiring harness, and the Display Board itself.

The most common points of failure in this circuit are loose or damaged connectors, particularly connector P1B on the power display and Display Board interface. Corrosion, a bent pin, or a partially seated connector can interrupt the Vcc rail without completely destroying any component. Wiring harness damage such as a pinched or frayed wire between the boards is another possibility, especially in ranges that have experienced heat exposure or physical stress during installation or service.

If the wiring and connectors check out and seat correctly without visible damage, the fault typically points to a failed Power Board that is no longer generating or supplying the correct Vcc output to the slave micro. In some cases the Display Board itself may have an internal failure on its input side that causes it to read the Vcc line as open even when voltage is present. The recommended diagnostic sequence is to inspect connector P1B and associated wiring first, replace the Power Board if wiring checks out, and replace the Display Board only if the fault persists after a Power Board swap.