Wolf Cooktop Code U400: Over Voltage on CI, CE and Integrated Modules

What U400 means

U400 means over voltage. It appears on Wolf CI induction cooktops from 2015 such as the CI304T/S and CI365T/S, on CE electric cooktops such as the CE304C/B and CE365T/S, and on the new 2015 integrated modules such as the CE152TF/S and CI152TF/S. The cooktop sees supply voltage above its limit and stops heating to protect itself. The same display can read differently on another Wolf model, and we say so plainly.

Common causes of U400

Supply voltage above the cooktop's limit
Utility or neighborhood voltage spike
Loose or wrong supply connection
Control board measuring voltage incorrectly

✓ One safe check you can try

1. Turn off all burners. 2. Switch the cooktop breaker off for a full minute and back on. 3. If U400 comes back, note whether lights or other appliances act oddly, which hints at a supply problem. 4. Call us. Do not open the unit or test the supply yourself.

! Why to stop there

Over voltage can come from the house, the utility or the cooktop, and live measurement is for a trained technician.
Repeated high voltage can damage a control board.
The written estimate arrives before the work does.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

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Other Cooktop codes

E7Wolf Induction Cooktop Code E7: Keyboard Diode Configuration Error E8Wolf CT Induction Code E8: no communication with generator 1 E9Wolf CT Cooktop Code E9: Generator 2 Communication Error E10Wolf Induction Code E10: generator 3 not responding to the control E53Wolf CT Cooktop Code E53: generator heat sink thermistor shorted E11Wolf CT Induction Code E11: A/D failure puts the cooktop in lock mode E54Wolf CT Induction E54 Code: Thermistor Short, Not a Pan Problem E12Wolf CT Cooktop Code E12: Universal OFF Key Failure

U400U400 questions

What does U400 mean?

It is an over voltage message. The cooktop measured more supply voltage than it allows and stopped heating. It is the same meaning on CI, CE and the 2015 integrated modules.

Will resetting the breaker fix U400?

Only if the high voltage was a one-time spike. If U400 returns, there is a lasting supply or control issue that needs measurement. A visit lets us confirm U400 in person, which keeps the repair focused.

Is it a cooktop problem or a house problem?

It can be either. We test on site, tell you which, and quote in writing before any repair. Our technician starts from U400 on the screen, and you decide after seeing the price.