--- title: "Bosch cooktop showing U400 | CooktopRepair.center" description: "What U400 means on Bosch cooktops, what to check before booking, and when it is not a failure at all." url: "https://cooktoprepair.center/error-codes/bosch-u400/" --- # Bosch cooktop showing U400 U400 reports a supply voltage that is too high or too low for the cooktop. ## What U400 actually means. U400 reports a supply voltage that is too high or too low for the cooktop. The problem sits in the circuit feeding the cutout, not in the zones. Bosch cooktop display What to do when U400 shows on the cooktop ### Kind of code Induction power and coils An induction zone could not drive its coil as the board planned: no pan was detected, the current ran too high or too low, or the power stage reported trouble. The pan base, the supply voltage and a clogged air intake are checked before the coil or the power board is replaced, and a top that trips its breaker is left switched off until then. ### Usually leads to Induction board and coil repair Induction zones that stop sensing pans, cut out, buzz or show codes, traced to the power boards, the coils, their sensors and the links to the controls. ### Shows up as Cooktop Tripping Breaker The circuit breaker for the cooktop trips as a burner or zone switches on, at one particular setting, or a few minutes into cooking. ### Make Bosch A German maker whose US site lists gas and induction cooktops for building into the counter. ### Source Bosch cooktop and rangetop error codes (US support) Listed for Bosch electric and induction cooktops; Bosch pairs it with E9011 for a wiring mistake. ## Before you book, in this order. Each step comes from Bosch's own guidance for U400 on its cooktops. Follow it to the end: the last card says whether this is a visit. 01 Switch the cooktop off at the breaker and leave it off. 02 Do not open the junction box below the cooktop yourself; leave the measurement to the electrician. 03 Have an electrician or the utility check the supply; book a visit once the voltage is known to be normal and U400 remains. ### Still there? It usually turns into [induction board and coil repair](https://cooktoprepair.center/services/induction-board-and-coil-repair/). Book with the code and the model number. ### What not to do U400 is not a pan or zone code, and using the cooktop anyway is not a fix. It is a report about the supply feeding the cooktop, which the cooktop cannot correct by itself. ## What you may notice with it. The cooktop problems U400 tends to arrive with. Answer these at the cooktop before anyone is booked. [All problems](https://cooktoprepair.center/problems/) Before you call ### [Cooktop Tripping Breaker](https://cooktoprepair.center/problems/cooktop-tripping-breaker/) [All 6 causes, cheapest first](https://cooktoprepair.center/problems/cooktop-tripping-breaker/) It also comes with - [**Cooktop Controls Unresponsive**](https://cooktoprepair.center/problems/cooktop-controls-unresponsive/) - [**Cooktop Error Code**](https://cooktoprepair.center/problems/cooktop-error-code/) Gas, fire, broken glass or live current ### Cooktop Tripping Breaker 6 causes, cheapest first Where U400 usually leads ## Induction board and coil repair. **Induction power board, coil or sensor · moderate to highest.** Book a visit [What the job involves](https://cooktoprepair.center/services/induction-board-and-coil-repair/) ## Bosch cooktops. A German maker whose US site lists gas and induction cooktops for building into the counter. [Bosch cooktop repair](https://cooktoprepair.center/brands/bosch/) More Bosch codes [dE](https://cooktoprepair.center/error-codes/bosch-de/) [F1](https://cooktoprepair.center/error-codes/bosch-f1/) [F2](https://cooktoprepair.center/error-codes/bosch-f2/) [F4](https://cooktoprepair.center/error-codes/bosch-f4/) [F5](https://cooktoprepair.center/error-codes/bosch-f5/) [F8](https://cooktoprepair.center/error-codes/bosch-f8/) [E9000](https://cooktoprepair.center/error-codes/bosch-e9000/) [E9011](https://cooktoprepair.center/error-codes/bosch-e9011/) [E7010](https://cooktoprepair.center/error-codes/bosch-e7010/) Induction power and coils on other makes [Bertazzoni U400](https://cooktoprepair.center/error-codes/bertazzoni-u400/) [Dacor C2](https://cooktoprepair.center/error-codes/dacor-c2/) [Fulgor Milano U400](https://cooktoprepair.center/error-codes/fulgor-milano-s700-u400/) [Gaggenau E9000](https://cooktoprepair.center/error-codes/gaggenau-e9000/) [KitchenAid FC E0](https://cooktoprepair.center/error-codes/kitchenaid-fc-e0/) [Samsung C2](https://cooktoprepair.center/error-codes/samsung-c2/) [SKS F33~F45](https://cooktoprepair.center/error-codes/sks-f33-f45/) [Thermador F9](https://cooktoprepair.center/error-codes/thermador-f9/) [All 23 codes of this kind](https://cooktoprepair.center/error-codes/#family-induction) Bosch builds this ### Gas cooktop A gas cooking surface dropped into a countertop cutout, with its gas line and power cord running down into the cabinet underneath. Bosch builds this ### Electric cooktop A coil or smooth-glass radiant cooking surface built into the countertop and wired to its own circuit in the cabinet or wall behind it. Bosch builds this ### Induction cooktop A glass cooktop in the counter that heats the pan itself through magnetic coils, run by power boards and cooled by a fan underneath. ## In Bosch's own words > The supply voltage is incorrect. It is outside the normal operating range. [Bosch cooktop and rangetop error codes (US support)](https://www.bosch-home.com/us/owner-support/error-codes/cooktops-and-rangetops) Every code on this site is taken from the manufacturer's documentation, never from a forum or a parts listing. Listed for Bosch electric and induction cooktops; Bosch pairs it with E9011 for a wiring mistake. ## Bosch U400 cooktop repair, where we come out. The same visit in every metro below: the code, the model number, and a diagnosis before any part is ordered. 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Switch the cooktop off at the breaker and leave it off. If it comes back, it needs a visit. ### Who should look at U400 on a Bosch cooktop first? The supply. Bosch points owners to the electrical utility; an electrician can measure the circuit at the junction box under the cooktop. ### Can a loose connection under the counter cause U400? A poor connection can distort the voltage the cooktop sees, which is why the check starts at the wiring below the cutout. ### Does Bosch pair U400 with E9011 for a reason? Both concern the power side of the cooktop rather than its zones. U400 reports a supply voltage outside the normal operating band, while E9011 means the cooktop is not connected to its circuit diagram correctly. An electrician checking one should look at the other. --- **[Read on the site: Bosch cooktop showing U400 | CooktopRepair.center](https://cooktoprepair.center/error-codes/bosch-u400/)** **[Book a visit with CooktopRepair.center](https://cooktoprepair.center/schedule/)**