Thermador Induction Range Cooktop U400: Supply Voltage Out of Range

What U400 means

On current Thermador induction ranges (Pro Harmony PRD...WIGU, PRI, Masterpiece MRI304DL), the manufacturer text for U400 matches E9000/E9010: the supply voltage is incorrect, outside the normal operating range. The legacy CIT365DS manual instead reads U400 as a cooktop connected incorrectly. We confirm which reading fits your unit on site. The code shows on the cooktop side.

Usual causes of U400

Supply voltage outside the normal operating range
Cooktop connected incorrectly (legacy CIT365DS reading)

✓ A safe check worth trying

1. Turn the cooktop off. 2. Reset the range breaker once, with the unit idle. 3. Think back: was the range moved, rewired or newly installed before U400 appeared? 4. If it stays, call us and mention that history; we confirm which reading applies.

! Why you should stop here

Two readings need a technician to tell apart.
Wiring checks are not owner work.
The price is written down first.

Taking off a panel yourself does not by default void a manufacturer warranty, yet it can lead to accidental damage, and some manufacturers attach their own service terms. Read your warranty paperwork, or ask us, before you decide.

→Same appliance

More Range codes

E11Older Thermador Pro-Harmony Range E11 and Light Code 44: Door Latch Problem E9000 / E9010Thermador Induction Range Cooktop E9000 / E9010: Supply Voltage Out of Range E12Thermador Pro-Harmony Range E12 (Light Code 11) - Expansion Board Not Connected F1 / F6Thermador Induction Range Cooktop F1 / F6: Cooking Zone Overheated E13What E13 Means on a Legacy Thermador PDR/PRG Range: Vcc Lift-Off, Code 13 F2 / E7015Thermador Induction Range Cooktop F2 / E7015: Electronics Overheated EThermador Range Display Reading "E" Plus a Number E14Thermador Pro-Harmony Range with Five-and-Five Blue Lights: E14 Selector Switch Error

U400U400 questions

Why are there two meanings?

The current manual says supply voltage, while the legacy CIT365DS manual says the cooktop was connected incorrectly. We check your model and wiring to see which one applies.

Is my cooktop the legacy kind?

Check the model number on the rating plate and send it to us. We confirm the generation before we quote anything. Please include any installation notes.

Can I use other zones meanwhile?

We would wait. With the voltage or connection unconfirmed, using the cooktop risks damaging the electronics, so book a check first. Ask us first. Book the check before cooking.